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
```