ColorPicker: Add a visual cue when the value is copied

[Mamaduka]

What?

Related #57157.

PR updates ColorPicker and adds a visual cue when the value is copied.

Why?

This is a common UI pattern, alongside changing the accessible label text.

Testing Instructions

1. Open a post or page.
2. Insert a paragraph block.
3. Select a color and open a color picker.
4. Confirm that the icon changes from copy to check when the value is copied.

Testing Instructions for Keyboard

Same.

Screenshots or screencast

CleanShot.2025-05-08.at.13.07.38.mp4

[github-actions]

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[github-actions]

Flaky tests detected in 54f0b10.
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/14903789453
📝 Reported issues:

• [Flaky Test] All navigation links should default to the body color and submenus and mobile overlay should default to a white background with black text #55304 in /test/e2e/specs/editor/blocks/navigation-colors.spec.js

[Mamaduka]

I'm going to merge this; it's a minor visual enhancement.