ControlWithError: Add docs about cloned children

[mirka]

What?

Adds documentation to the ControlWithError component explaining how it handles cloned children.

Why?

The ControlWithError component clones its child element to inject enhanced props, but this behavior wasn't documented. This is important because certain behavior will not work if the root-level component of children doesn't handle these injected props (for example if there's a wrapper div around the main control that doesn't forward the necessary props — which happened in #71350 (comment)).

[github-actions]

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Co-authored-by: mirka <0mirka00@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>

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[tyxla]

👍 Thanks!

[github-actions]

Flaky tests detected in 4b6f8f4.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/17307737882
📝 Reported issues:

• [Flaky Test] ensures List View global shortcut works properly #51533 in /test/e2e/specs/editor/various/list-view.spec.js
• [Flaky Test] should hide the toolbar when typing #48859 in /test/e2e/specs/editor/various/is-typing.spec.js