Add kernel tests for hook system

The kernel tests are based on the unit tests in 📌 Improve unit test coverage for ModuleHandler RTBC .
Some methods are not converted yet.

I already tested how the test will change with the Hux MR.
Most of it remains unchanged, because we don't rely on mocks, and we use the real service definitions, instead of custom composition.

There is one commit borrowed from 📌 Add kernel tests for event system RTBC .

Maybe we can drop some parts of Drupal\Tests\Core\Extension\ModuleHandlerTest?
Not sure.

This MR introduces other changes:

• Possibility to declare test module names per test method, using an attribute.
• Possibility to use "fake" modules that do not actually exist in the file system.

This works, but needs to be cleaned up a bit and made universally usable by all tests.

It would be interesting to have virtual modules in stream wrappers.
To do this we need to allow modules to have a different root path.

Was hoping 📌 Establish "core/tests/$type" as a canonical place for test extensions Needs work would land first but I'll go ahead and mark this. If this lands before guess the other could be closed.

I'm triaging RTBC issues → . I read the IS, the comments and the MR (not a code review).

Always good to improve testing, thanks!

Comment #7 states "This works, but needs to be cleaned up a bit and made universally usable by all tests." It seems this should be at needs work?

I left some comments in the MR, mostly about comments. However, I see that this is adding a word to the dictionary. We should not be doing that and I have asked a question about that. Because of that, and possibly #7, I am setting this back to needs work.