[DI] Add "by-id" autowiring: a side-effect free variant of it based on the class<>id convention

[javiereguiluz]

See symfony/symfony#22060

[weaverryan]

Actually, this is more important now - as we're introducing a BC break in 3.3 related to this: symfony/symfony#22295

[weaverryan]

The BC break is gone, but it's now the preferred way to explicitly define all services (and not let autowiring automatically create them for you)

[HeahDude]

Closing here as fixed by #7807 which is now merged.