Automatic merge from submit-queue
Note equivalence class for dev and other fix
**What this PR does / why we need it**:
1. Add a note for predicate developers to respect equivalence class design
2. Add comments and re-ordered the related data structure, ref https://github.com/kubernetes/community/pull/1031
3. Fix some nits (typo, code length etc)
**Special notes for your reviewer**:
**Release note**:
```release-note
Scheduler predicate developer should respect equivalence class cache
```
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