Automatic merge from submit-queue

[Part 1] Implementation of equivalence pod

Part 1 of #30844

This PR: 

- Refactored `predicate.go`, so that `GetResourceRequest` can be used in other places to `GetEquivalencePod`.
- Implement a `equivalence_cache.go` to deal with all information we need to calculate an equivalent pod.
- Define and register a `RegisterGetEquivalencePodFunction `.

Work in next PR:
- The update of `equivalence_cache.go`
- Unit test
- Integration/e2e test

I think we can begin from the `equivalence_cache.go`? Thanks.  cc @wojtek-t @davidopp 

If I missed any other necessary part, please point it out.