Automatic merge from submit-queue (batch tested with PRs 65256, 64236, 64919, 64879, 57932). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Move equivalence cache to its own package
**What this PR does / why we need it**:
Untangle equivalence class implementation from genericScheduler implementation. This makes it clearer where the two interact, and prevents them from accessing unexported internals.
**Special notes for your reviewer**:
Please review https://github.com/kubernetes/kubernetes/pull/63942 first as this is based on it.
This also needs to rebase on https://github.com/kubernetes/kubernetes/pull/64216 to pass tests.
**Release note**:
```release-note
NONE
```
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