Block Bindings: Add support for Media & Text block image

[theminaldiwan]

This PR adds block bindings support for the Media & Text block’s mediaId attribute. as this issue mentioned in #68637
With this change, the image inside the Media & Text block can be dynamically sourced (e.g., post featured image, custom fields, or other bindings), rather than being limited to a fixed image or the featured image only.

Why?

Currently, the Media & Text block is useful in templates but restricted in flexibility since the image must either be manually uploaded or set to the featured image.
By enabling block bindings on the mediaId, template authors and developers can connect the block to other dynamic image sources (e.g., post meta, custom fields, reusable bindings), making it far more versatile for building dynamic templates.

How?

• Added bindings support to the mediaId attribute of the Media & Text block.

And we need to below pattern code

<!-- wp:media-text {"blockBindings":{"mediaId":{"source":"core/post-featured-image"}}} -->
<div class="wp-block-media-text is-stacked-on-mobile">
    <figure class="wp-block-media-text__media"></figure>
    <div class="wp-block-media-text__content">
        <p>This should now display the Featured Image.</p>
    </div>
</div>
<!-- /wp:media-text -->

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[cbravobernal]

Hi there!

Thanks for contributing. Unfortunately, the code you provided won't make those block attributes bindables 😅 . Please take a look at this PR:

#70642

That won't be merged, but adding new block attributes should be done similarly to that one.

[t-hamano]

@theminaldiwan thanks for the PR!

Let's close this PR for now and try a recommended approach if needed.