Post and comment likes: make them fully block-based

### Impacted plugin

Jetpack

### What

Fully support Like and Comment Like blocks instead of the_content/comment_text filters

### How

If you go to Jetpack Sharing settings, the "Sharing buttons" feature warns you that you're dealing with a legacy feature and that you should use the "Sharing Buttons" block.

The "Like buttons" feature doesn't show such a warning. But it should 🙂

When I enable the `likes` or `comment-likes` module/feature, two things happen:
1. the module extends the wp-admin view for posts/comments by adding a column with likes.
2. the module hooks into the `the_content`/`the_excerpt`/`comment_text` filters and adds the post/comment Like widget to the markup.

There should be a possibility to:
1. Keep the wp-admin extensions.
2. Disable the filters and add the "Like" and "Comment Like" buttons by adding the respective blocks to my templates.

Currently this is not possible: if I have "Like buttons" enabled and I add the "Like" block to my template, I will see the "Like" button twice. The "legacy" and "block-based" Likes don't work together well.

Additionally, the "Comment Like" block currently doesn't exist at all, it's a feature gap.

Start with the Jetpack likes and comment-likes modules, the wp-admin post/comment extensions, and their the_content, the_excerpt, and comment_text filters. Trace how the existing Like block is registered and where the missing Comment Like block belongs; done means templates can use the blocks without duplicate legacy buttons while the admin like columns remain available.

Written by the indexing model from the issue text.