…stom transports (Koc)

This PR was merged into the 4.4 branch.

Discussion
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[Mailer] Extract transport factory and allow create custom transports

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes, failure unrelated (master hasn't this PR)
| Fixed tickets | #31385, #32523
| License       | MIT
| Doc PR        | TBD

Alternative approach to allow create custom transports and register DSN for it. Replaces #31931, #31935 . Similar to already existent TansportFactory from Messenger.

TODO:
 - [x] Update changelog
 - [x] Add more tests for factories
 - [x] Add test for configuration + DI extension

Commits
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5b9cded Add transport factories (closes #31385, closes #32523)

* 4.4:
  [WebProfilerBundle] Remove unneeded information in the routing panel
  Add transport factories (closes #31385, closes #32523)
  [Lock] remove uusage of the StoreInterface
  [HttpClient] make toStream() throw by default
  [Mailer] added XML configuration for the mailer envelope
  added missing test
  [Mailer] Allow register mailer configuration in xml format
  [VarDumper] Allow to configure VarDumperTestTrait casters & flags
  Improve errors when trying to find a writable property
  [Lock] add aliases for LockFactory
  fixed CS
  fix some deprecations and add upgrade instructions
  fix typo
  Added Nl translations
  fixed CS
  [FrameworkBundle] Fix descriptor of routes described as callable array
  [Debug][DebugClassLoader] Include found files instead of requiring them
  [HttpKernel] fix tests
  Adding missing event_dispatcher wiring for messenger.middleware.send_message