Automatic merge from submit-queue (batch tested with PRs 38676, 41765, 42103, 41833, 41702)
Support --context flag completion for kubectl
**What this PR does / why we need it**:
With this PR, `--context` flag completion is supported for kubectl.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
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