feat: Add parameter to display featured image caption

[efu98]

What?

Add an option to display caption on featured image block

Why?

Closes #40946

How?

Added a new toggle control to display featured image caption

Testing Instructions

1. Upload an image
2. Add a caption to the image
3. Open a post or page
4. Set the featured image to the image you've just uploaded
5. Enable "Display caption"

Testing Instructions for Keyboard

Screenshots or screencast

[github-actions]

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Unlinked contributors: kaffeeringe, greening, jethin, janvitos, kevinpoot, belisama, supernovia, dhanson-wp, noellesteegs, jordonrupp-dev.

Co-authored-by: efu98 <elfu98@git.wordpress.org>
Co-authored-by: hagege <hage@git.wordpress.org>
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[github-actions]

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