Automatic merge from submit-queue (batch tested with PRs 48123, 48079)
kubectl/cmd: many small refactors
#### Improve Code Quality in `pkg/kubectl/cmd`
___
* [x] Rename variables and functions to match Go convention. For example, UsageError --> UsageErrorf.
* [x] Remove redundant or unreachable code.
* [x] Simplify some utility functions (no functionality changes).
* [x] Fix hanging 'if { return } else { return }' constructs.
* [x] Fix several incorrect printf verbs.
These changes were extracted from the refactoring and flag parity work I'm doing in kubectl.
**Release note**:
```release-note
NONE
```
18e8bedb2b