Automatic merge from submit-queue (batch tested with PRs 48264, 48324, 48125, 47944, 47489)
Add Pod UID (metadata.uid) to downward API env var
**What this PR does / why we need it**:
Exposing Pod UID by downward API.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#28918
**Special notes for your reviewer**:
Generated files aren't committed. I'd like CI to tell me what scripts should I run to generate these files.
/cc @smarterclayton @vishh @dubstack
**Release note**:
```release-note
NONE
```
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