Simplify the block bindings HTML replacement logic until the HTML API is ready

[SantosGuillamot]

Trac ticket: https://core.trac.wordpress.org/ticket/61351

Backport of the following PRs: #61236 and #61660

What?

Change the block bindings HTML replacement logic to use a hardcoded list of selectors based on the block and a regex to substitute the inner content.

Apart from that, it removes some extra breaks that are not needed.

Why?

The existing logic is too complex because the HTML API doesn't support CSS selectors yet and it doesn't have an official way to modify the inner HTML. This makes it difficult to understand, iterate on it and add new functionalities.

As it will be solved in the future once the HTML API is ready, I believe it is better to keep a simple hardcoded version that is easier to understand and iterate on.

How?

• Change the selector based on the supported blocks.
• Using a regex, replace the inner content.

Testing Instructions

0. Register a custom field in your site to test it. You can use a code snippet like this:

register_meta(
	'post',
	'text_custom_field',
	array(
		'show_in_rest' => true,
		'single'       => true,
		'type'         => 'string',
		'default'	   => 'default value',
	)
);

1. Go to a page and insert a paragraph block.
2. Go to the Code editor and connect the paragraph to the custom field by adding the metadata bindings property. It should look something like this:

<!-- wp:paragraph {"metadata":{"bindings":{"content":{"source":"core/post-meta","args":{"key":"text_custom_field"}}}}} -->
<p>Original content</p>
<!-- /wp:paragraph -->

3. Save the page and check that in the frontend, the text defined in the custom field is used.
4. Repeat the process for heading, and button blocks.

---

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[audrasjb]

committed in https://core.trac.wordpress.org/changeset/58298