Fix: Embed blocks: figcaption inserted via toolbar not nested within figure element - #64960

[hbhalodia]

What?

• Issue - Embed blocks: figcaption inserted via toolbar not nested within figure element #64960

Why?

• This would fix the issue stated here - Embed blocks: figcaption inserted via toolbar not nested within figure element #64960,

How?

• PR refactors the embed block to use caption inside embed preview for editor, so that figcaption adds as a child of figure instead of sibling.

Testing Instructions

1. Add embed block.
2. Add the caption.
3. Inspect the caption element, and you can see figcaption added as a child of figure.

Testing Instructions for Keyboard

• NIL

Screenshots or screencast

GB-Issue-64960.mov

[github-actions]

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Co-authored-by: hbhalodia <hbhalodia@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>

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[t-hamano]

LGTM! Works as expected 👍