Add integration tests for detecting CRD installed after Kueue started

[mimowo]

What would you like to be cleaned:

This is a follow up to https://github.com/kubernetes-sigs/kueue/pull/2574.

Why is this needed:

To gain confidence the mechanism works as expected since there are pieces of the code which are hard to cover with unit tests.

[mimowo]

/cc @ChristianZaccaria @varshaprasad96 @alculquicondor @tenzen-y

[tenzen-y]

That makes sense. Since we implemented the watcher by hand, we should keep to prove that the watcher works fine.

[mbobrovskyi]

/assign