[DI] add tags container.preload/.no_preload to declare extra classes to preload/services to not preload

[nicolas-grekas]

Q	A
Branch?	master
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	-
License	MIT
Doc PR	-

To allow fine-grained declaration of sidekick classes in DI extensions.
Follows #36103

[michaljusiega]

So class_exists is no longer needed in favor of container.preload tag do add classes to *.preload.php dumped file ?

[stof]

@michaljusiega AFAIU, the class_exists were solving 2 issues:

• discovery of classes to be preloaded
• compatibility with preloading is some specific cases related to anonymous classes which break if the class is not loaded

This PR provides an alternative solution to the first issue (though class_exists will still work). For the second problem, class_exists is still the proper solution IMO, as that's not about the Symfony preload dumper by itself, but about compat with preloading.

[nicolas-grekas]

I updated the PR to now also provide a container.no_preload tag.
I added it to eg. console commands.

@michaljusiega: what @stof said: class_exists() are better options for portability and for locality. container.preload serves adding preloading info to third party packages that don't (want to) use class_exists(), and also in programmatic situations where a bundle's logic might known better about fine grained preloading, depending on the configuration.

[michaljusiega]

@nicolas-grekas, @stof I understand. Thanks!

[fabpot]

Thank you @nicolas-grekas.