kubectl-drain: add page

[girdharagrawalbro]

Adds documentation for the kubectl drain subcommand used for node maintenance.

Closes part of #17606 (kubectl cluster management commands).

Changes

• Created pages/common/kubectl-drain.md with 5 practical examples
• Covers common maintenance scenarios: basic drain, force delete, emptyDir handling
• Includes control-plane node example and label selector usage
• Follows style guide: imperative mood, clear descriptions, proper placeholder syntax

Examples

• Drain a node with PodDisruptionBudgets
• Force delete standalone pods
• Delete pods using emptyDir volumes
• Drain control-plane nodes
• Drain by label selector

[CLAassistant]

All committers have signed the CLA.

[trolzen]

Hello, @girdharagrawalbro! Are you using some kind of AI tool to craft the pages and PR descriptions?

[Managor]

He most certainly is. That is not a problem as long as the commands work. The trouble starts when the submitter submits a PR with hallucinations.

[trolzen]

Yeah, that is my concern, too. If that's the case, I was going to ask them if they put an extra effort to double-check the output before submitting. Now it look like not so much, as there are many change requests from the reviewers, mostly covered by the style guide.