…kas)

This PR was merged into the 3.3 branch.

Discussion
----------

[DI] Fix reading env vars from fastcgi params

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #23348
| License       | MIT
| Doc PR        | -

Values in fastcgi_param populate `$_SERVER`, never `$_ENV`.
This PR makes `$container->getEnv()` read from `$_SERVER`, excluding any vars whose name start by `HTTP_` as that would be a security issue (values injection via HTTP headers.)

Embeds a few other fixes found meanwhile.

Commits
-------

adff65a [DI] Fix reading env vars from fastcgi params

This PR was merged into the 3.4 branch.

Discussion
----------

[DI] Allow processing env vars

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | see description
| License       | MIT
| Doc PR        | -

This PR is an updated version of #20276 ~~(it embeds #23899 for now.)~~

It superscedes/closes:
- [DI] Add support for secrets #23621 ping @dunglas
- Runtime container parameter not found event filter #23669 ping @marfillaster
- [DependencyInjection] [DX] Support for JSON string environment variables #23823 ping @Pierstoval
- add support for composite environment variables #17689 ping @greg0ire
- [DI] ENV parameters at runtime with PHP 7 strict types not working properly #20434 ping @sandrokeil
- Issue when using a SQLite database and the DATABASE_URL env var #23527 ping @javiereguiluz

#22151 is another story, so not fixed here.

The way it works is via `%env(foo:BAR)%` prefixes, where "foo" can be bound to any services you'd like.
By default, the following prefixes are supported:
- `bool`, `int`, `float`, `string`, `base64`
- `const` (for referencing PHP constants)
- `json` (supporting only json **arrays** for type predictability)
- `file` (eg for access to secrets stored in files.)
- `resolve` (for processing parameters inside env vars.)

New prefixes can be added by implementing the new `EnvProviderInterface`, and tagging with `container.env_provider` (see `Rot13EnvProvider` in tests.)

Prefixes can be combined to chain processing, eg.
`%env(json:base64:file:FOO)%` will be roughly equivalent to
`json_decode(base64_decode(file_get_content(getenv('FOO'))))`.

Commits
-------

1f92e45 [DI] Allow processing env vars