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
```