Automatic merge from submit-queue (batch tested with PRs 62425, 62212, 60824, 62383, 62384). 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>.
optimize requestcontext: use RWMutex to improve r/w performance
RequestContextMapper is one of the mostly used interface by every request, and the underlying struct is a map with Mutex protect. So here we should use RWMutex.
**Release note**:
```release-note
NONE
```
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