Automatic merge from submit-queue (batch tested with PRs 64597, 67854, 67734, 67917, 67688). 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>.
fix an issue that scheduling doesn't respect NodeLost status of a node
**What this PR does / why we need it**:
- if Node is in UnknowStatus, apply unreachable taint with NoSchedule effect
- some internal data structure refactoring
- update unit test
**Which issue(s) this PR fixes**:
Fixes#67733, and very likely #67536
**Special notes for your reviewer**:
See detailed reproducing steps in #67733.
**Release note**:
```release-note
Apply unreachable taint to a node when it lost network connection.
```
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