Description

Resolves: #28736
Part of: #27575

This is a POC for suggesting block pattern transformations that are contextual to the currently selected blocks.

First of all we need to decide what type of transformations we will suggest/support and we have to keep in mind flows for template parts and any other special cases we can think of. You can find discussions on the above issues and especially here.

Rationale behind the current decisions

1. While it makes sense to show patterns for grouping blocks (like Group or Columns) during insertion in Placeholder (explored here), it doesn't make sense to suggest any pattern to transform, as a user could have anything inside as content. So if any selected block falls into this category, do not suggest any transforms.
2. The only exception to the above would be Template Parts (at least from what I thought) and we should have a replacing all contents flow probably.
3. I have skipped any check about transforming selected blocks to available block transforms inside patterns, as I think it would be very confusing to have a really different suggested pattern. An example would be to have a paragraph selected and show patterns that do not include paragraph but have transformed the paragraph to a quote block.
4. To show a suggested pattern, every selected block must have matched with a pattern's block . This doesn't necessarily mean that the order will be preserved. You can test this in this PR by selecting a paragraph and two headings (in this order) and see the suggested pattern that has the following order: [heading, paragraph, heading]. Also shown at the gif.
5. If a suggested pattern has more blocks than the selected blocks, add them as are from the pattern. Every pattern block that matched with a selected block will be transformed. IMO this is the main reason for doing this and having block patterns in general. We want to inspire/show users alternative designs.

I have many comments in my code trying to explain as good as I can the flows.

Testing instructions

1. Test with the demo patterns I created in lib/test-block-patterns.php or register one yourselves
2. Create some paragraphs or headings and make different selections (single or multiple) to observe the previews from the selected blocks.
3. Only if all of the selected blocks can be matched in pattern's blocks, it will be shown as an option

Screenshots

Notes

1. I would like some feedback/thoughts about the handling of patterns transformation first, so design wise focus on a higher level and not details that can be fixed quite easily.
2. There has been some POC work for Template Parts to take into account active variations, but the flow is not complete. We will probably need to create a new Template Part on a selection.

I would love your thoughts and feedback on this!

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.