Remove anchor support from dynamic blocks

[t-hamano]

Fixes: #48232
Fixes: #49382
Fixes: #49578

Related to: #48438

What?

This PR reverts anchor support for dynamic blocks added by #44771.

Why?

In #44771, anchor support was added to dynamic blocks, but static blocks with existing anchor were broken (See #48232, #49382, and #49578). This feature was originally planned to be included in WordPress 6.2, but #48232 was the first to report this issue during the Beta phase. Therefore, by #48592, this feature was excluded in the WordPress 6.2 release.

However, this feature still remains on the Gutenberg plugin, which will be bundled with WordPress 6.3 and will cause similar problems. A solution was attempted in #48438, but we decided to revert anchor support for dynamic blocks in the Gutenberg plugin as well, in order to find a more ideal solution.

How?

Strikes out the changes made in #44771 as is, removing anchor support for a total of 53 dynamic blocks. After #44771 was merged, a new Time To Read block was added. However, this block does not currently support anchor, so it does not need to be considered in this PR.

Testing Instructions

• To test the impact of this PR, the following four types of blocks should be tested:
  • Static block without anchor
  • Static block with anchor
  • Dynamic block without anchor
  • Dynamic block with anchor
• In the trunk branch, insert all types of blocks as follows:

  <!-- wp:paragraph -->
  <p>Static block without anchor</p>
  <!-- /wp:paragraph -->
  
  <!-- wp:paragraph {"anchor":"anchor"} -->
  <p id="anchor">Static block with anchor</p>
  <!-- /wp:paragraph -->
  
  <!-- wp:site-title /-->
  
  <!-- wp:site-title {"anchor":"anchor"} /-->

• Switch to this PR branch and reload the editor. There should be no blocks to be broken.
• Open the Advanced tab of the dynamic block and confirm that the HTML ANCHOR is not present.
• Make changes to the content, save the post, and reload. There should be no blocks to be broken.
• Open the code editor and confirm that the saved markup has changed as follows:

  <!-- wp:paragraph -->
  <p>Static block without anchor</p>
  <!-- /wp:paragraph -->
  
  <!-- wp:paragraph -->
  <p id="anchor">Static block with anchor</p>
  <!-- /wp:paragraph -->
  
  <!-- wp:site-title /-->
  
  <!-- wp:site-title /-->

[aaronrobertshaw]

Nice work @t-hamano 👍

The changes here revert those made in #44771 and it all tests well for me following the test instructions.

I'm happy to approve this but it might be good to get a double-check from @Soean who authored the original PR.

[t-hamano]

Note: This PR contains changes to PHP files, but a similar PR has already been merged into the wp/6.2 branch (#48592). I also checked the trunk branch of WP core just to be sure, but the PHP files and lines deleted in this PR do not exist in WP core. Therefore, I think no PHP backport should be necessary.

[ramonjd]

Thanks @t-hamano

I'll remove #44771 from the list of PHP changes to be backported to Core for 6.3

👍