Refactor Matching and Route Filters.

This overhaul introduces a NestedMatcher option, inspired by Drupal 8, a RouteProvider to replace RouteRespository, and Router Enhancers to post-process a found route.  It does contain some BC breaks, but results in a much cleaner and more reusable component.

This PR was merged into the 5.2-dev branch.

Discussion
----------

[VarDumper] Support for ReflectionAttribute

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | not needed

VarDumper currently does not understand that certain reflection objects might have attributes attached to it. Dumping a `ReflectionAttribute` just yields `ReflectionAttribute {#4711}` which is not really helpful. This PR attempts to fix this.

```
ReflectionAttribute {#4711
  name: "App\MyAttribute"
  arguments: array:2 [
    0 => "one"
    "extra" => "hello"
  ]
}
```

While working on this, I noticed that class constants (which can be reflected on since PHP 7.1) are just dumped as plain values, so I've also added a caster for `ReflectionClasConstant` as bonus.

The full output for the `LotsOfAttributes` fixture class that is included with is PR looks like this:

<details>

```
^ ReflectionClass {#7
  +name: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
  modifiers: "final"
  implements: []
  constants: array:1 [
    0 => ReflectionClassConstant {#20
      +name: "SOME_CONSTANT"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      modifiers: "public"
      value: "some value"
      attributes: array:2 [
        0 => ReflectionAttribute {#33
          name: "Symfony\Component\VarDumper\Tests\Fixtures\RepeatableAttribute"
          arguments: array:1 [
            0 => "one"
          ]
        }
        1 => ReflectionAttribute {#34
          name: "Symfony\Component\VarDumper\Tests\Fixtures\RepeatableAttribute"
          arguments: array:1 [
            0 => "two"
          ]
        }
      ]
    }
  ]
  properties: array:1 [
    "someProperty" => ReflectionProperty {#19
      +name: "someProperty"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      modifiers: "private"
      attributes: array:1 [
        0 => ReflectionAttribute {#30
          name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
          arguments: array:2 [
            0 => "one"
            "extra" => "hello"
          ]
        }
      ]
    }
  ]
  methods: array:1 [
    "someMethod" => ReflectionMethod {#21
      +name: "someMethod"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      returnType: "void"
      parameters: {
        $someParameter: ReflectionParameter {#28
          +name: "someParameter"
          position: 0
          attributes: array:1 [
            0 => ReflectionAttribute {#42
              name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
              arguments: array:1 [
                0 => "three"
              ]
            }
          ]
          typeHint: "string"
        }
      }
      attributes: array:1 [
        0 => ReflectionAttribute {#27
          name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
          arguments: array:1 [
            0 => "two"
          ]
        }
      ]
      modifiers: "public"
    }
  ]
  attributes: array:1 [
    0 => ReflectionAttribute {#22
      name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
      arguments: []
    }
  ]
  extra: {
    file: "./src/Symfony/Component/VarDumper/Tests/Fixtures/LotsOfAttributes.php"
    line: "15 to 28"
    isUserDefined: true
  }
}
```

</details>

Commits
-------

34dbf01 [VarDumper] Support for ReflectionAttribute.

…lishing a message. (jwage)

This PR was squashed before being merged into the 6.4 branch.

Discussion
----------

[Messenger] [Amqp] Handle AMQPConnectionException when publishing a message.

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix #36538 Fix #48241
| License       | MIT

If you have a message handler that dispatches messages to another queue, you can encounter `AMQPConnectionException` with the message "Library error: a SSL error occurred" or "a socket error occurred"  depending on if you are using tls or not or if you are running behind a load balancer or not.

You can manually reproduce this issue by dispatching a message where the handler then dispatches another message to a different queue, then go to rabbitmq admin and close the connection manually, then dispatch another message and when the message handler goes to dispatch the other message, you will get this exception:

```
a socket error occurred
#0 /vagrant/vendor/symfony/amqp-messenger/Transport/AmqpTransport.php(60): Symfony\Component\Messenger\Bridge\Amqp\Transport\AmqpSender->send()
#1 /vagrant/vendor/symfony/messenger/Middleware/SendMessageMiddleware.php(62): Symfony\Component\Messenger\Bridge\Amqp\Transport\AmqpTransport->send()
#2 /vagrant/vendor/symfony/messenger/Middleware/FailedMessageProcessingMiddleware.php(34): Symfony\Component\Messenger\Middleware\SendMessageMiddleware->handle()
#3 /vagrant/vendor/symfony/messenger/Middleware/DispatchAfterCurrentBusMiddleware.php(61): Symfony\Component\Messenger\Middleware\FailedMessageProcessingMiddleware->handle()
#4 /vagrant/vendor/symfony/messenger/Middleware/RejectRedeliveredMessageMiddleware.php(41): Symfony\Component\Messenger\Middleware\DispatchAfterCurrentBusMiddleware->handle()
#5 /vagrant/vendor/symfony/messenger/Middleware/AddBusNameStampMiddleware.php(37): Symfony\Component\Messenger\Middleware\RejectRedeliveredMessageMiddleware->handle()
#6 /vagrant/vendor/symfony/messenger/Middleware/TraceableMiddleware.php(40): Symfony\Component\Messenger\Middleware\AddBusNameStampMiddleware->handle()
#7 /vagrant/vendor/symfony/messenger/MessageBus.php(70): Symfony\Component\Messenger\Middleware\TraceableMiddleware->handle()
#8 /vagrant/vendor/symfony/messenger/TraceableMessageBus.php(38): Symfony\Component\Messenger\MessageBus->dispatch()
#9 /vagrant/src/Messenger/MessageBus.php(37): Symfony\Component\Messenger\TraceableMessageBus->dispatch()
#10 /vagrant/vendor/symfony/mailer/Mailer.php(66): App\Messenger\MessageBus->dispatch()
#11 /vagrant/src/Mailer/Mailer.php(83): Symfony\Component\Mailer\Mailer->send()
#12 /vagrant/src/Mailer/Mailer.php(96): App\Mailer\Mailer->send()
#13 /vagrant/src/MessageHandler/Trading/StrategySubscriptionMessageHandler.php(118): App\Mailer\Mailer->sendEmail()
#14 /vagrant/src/MessageHandler/Trading/StrategySubscriptionMessageHandler.php(72): App\MessageHandler\Trading\StrategySubscriptionMessageHandler->handle()
#15 /vagrant/vendor/symfony/messenger/Middleware/HandleMessageMiddleware.php(152): App\MessageHandler\Trading\StrategySubscriptionMessageHandler->__invoke()
#16 /vagrant/vendor/symfony/messenger/Middleware/HandleMessageMiddleware.php(91): Symfony\Component\Messenger\Middleware\HandleMessageMiddleware->callHandler()
#17 /vagrant/vendor/symfony/messenger/Middleware/SendMessageMiddleware.php(71): Symfony\Component\Messenger\Middleware\HandleMessageMiddleware->handle()
#18 /vagrant/vendor/symfony/messenger/Middleware/FailedMessageProcessingMiddleware.php(34): Symfony\Component\Messenger\Middleware\SendMessageMiddleware->handle()
#19 /vagrant/vendor/symfony/messenger/Middleware/DispatchAfterCurrentBusMiddleware.php(68): Symfony\Component\Messenger\Middleware\FailedMessageProcessingMiddleware->handle()
#20 /vagrant/vendor/symfony/messenger/Middleware/RejectRedeliveredMessageMiddleware.php(41): Symfony\Component\Messenger\Middleware\DispatchAfterCurrentBusMiddleware->handle()
#21 /vagrant/vendor/symfony/messenger/Middleware/AddBusNameStampMiddleware.php(37): Symfony\Component\Messenger\Middleware\RejectRedeliveredMessageMiddleware->handle()
#22 /vagrant/vendor/symfony/messenger/Middleware/TraceableMiddleware.php(40): Symfony\Component\Messenger\Middleware\AddBusNameStampMiddleware->handle()
#23 /vagrant/vendor/symfony/messenger/MessageBus.php(70): Symfony\Component\Messenger\Middleware\TraceableMiddleware->handle()
#24 /vagrant/vendor/symfony/messenger/TraceableMessageBus.php(38): Symfony\Component\Messenger\MessageBus->dispatch()
#25 /vagrant/vendor/symfony/messenger/RoutableMessageBus.php(54): Symfony\Component\Messenger\TraceableMessageBus->dispatch()
#26 /vagrant/vendor/symfony/messenger/Worker.php(162): Symfony\Component\Messenger\RoutableMessageBus->dispatch()
#27 /vagrant/vendor/symfony/messenger/Worker.php(109): Symfony\Component\Messenger\Worker->handleMessage()
#28 /vagrant/vendor/symfony/messenger/Command/ConsumeMessagesCommand.php(238): Symfony\Component\Messenger\Worker->run()
#29 /vagrant/vendor/symfony/console/Command/Command.php(326): Symfony\Component\Messenger\Command\ConsumeMessagesCommand->execute()
#30 /vagrant/vendor/symfony/console/Application.php(1096): Symfony\Component\Console\Command\Command->run()
#31 /vagrant/vendor/symfony/framework-bundle/Console/Application.php(126): Symfony\Component\Console\Application->doRunCommand()
#32 /vagrant/vendor/symfony/console/Application.php(324): Symfony\Bundle\FrameworkBundle\Console\Application->doRunCommand()
#33 /vagrant/vendor/symfony/framework-bundle/Console/Application.php(80): Symfony\Component\Console\Application->doRun()
#34 /vagrant/vendor/symfony/console/Application.php(175): Symfony\Bundle\FrameworkBundle\Console\Application->doRun()
#35 /vagrant/vendor/symfony/runtime/Runner/Symfony/ConsoleApplicationRunner.php(49): Symfony\Component\Console\Application->run()
#36 /vagrant/vendor/autoload_runtime.php(29): Symfony\Component\Runtime\Runner\Symfony\ConsoleApplicationRunner->run()
#37 /vagrant/bin/console(11): require_once('...')
#38 {main}
```

TODO:

- [x] Add test for retry logic when publishing messages

Commits
-------

f123370 [Messenger] [Amqp] Handle AMQPConnectionException when publishing a message.

Make bundle compatible with Symfony 4