…rs synchronously (weaverryan)

This PR was merged into the 4.3-dev branch.

Discussion
----------

[Messenger] Adding the "sync" transport to call handlers synchronously

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | symfony/symfony-docs#11236

This adds a `sync://` transport that just calls the handlers immediately. Why? This allows you to route your messages to some "async" transport. But then, when developing locally or running your tests, you can choose to run them synchronously instead:

```yml
# config/packages/messenger.yaml
framework:
    messenger:
        transports:
            async: '%env(MESSENGER_TRANSPORT_DSN)%'
        routing:
            'App\Message\SmsNotification': async
            'App\Message\OtherMessage': async
```

```
# .env
# by default, handle this sync
MESSENGER_TRANSPORT_DSN=sync://
```

```
# .env.local on production (or set this via real env vars)
# on production, use amqp
MESSENGER_TRANSPORT_DSN=amqp://.......
```

Cheers!

Commits
-------

3da5a43 Adding the "sync" transport to call handlers synchronously

…ed with SyncTransport (Tobion)

This PR was merged into the 4.3 branch.

Discussion
----------

[Messenger] remove send_and_handle which can be achieved with SyncTransport

| Q             | A
| ------------- | ---
| Branch?       | 4.3
| Bug fix?      | no
| New feature?  | yes/no <!-- please update src/**/CHANGELOG.md files -->
| BC breaks?    | yes     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets |
| License       | MIT
| Doc PR        | symfony/symfony-docs#11236

The send_and_handle option is pretty awkward and we don't need it anymore because the same thing can be achieved with the SyncTransport from #30759

So the following example from the doc in https://symfony.com/doc/current/messenger.html#routing
```yaml
framework:
    messenger:
        routing:
            'My\Message\ThatIsGoingToBeSentAndHandledLocally':
                 senders: [amqp]
                 send_and_handle: true
```
is the same as
```yaml
framework:
    messenger:
        routing:
            'My\Message\ThatIsGoingToBeSentAndHandledLocally':
                 senders: [amqp, sync]
```

#31401 (review)

Commits
-------

4552b7f [Messenger] remove send_and_handle option which can be achieved with SyncTransport