[WIP] Block Supports: Try stabilizing common experimental block support flags

[aaronrobertshaw]

⚠️ ⚠️ This PR is incomplete and not ready for review⚠️ ⚠️

Depends on:

• Borders: Stabilize border block supports within block processing #66918

What?

Extends the approach to block support stabilization in #66918 to also stabilize shared/common experimental block support flags such as:

• __experimentalSkipSerialization
• __experimentalDefaultControls

Why?

These experimental flags have been around a long time and are extensively used throughout core blocks. It's time to stabilize them to increase confidence for extenders and better document what is possible.

How?

• Leverages the same block type args filter as Borders: Stabilize border block supports within block processing #66918 and Typography: Stabilize typography block supports within block processing #63401.
• Updates the filter's algorithm to stabilize shared experimental keys
• Keeps __experimentalSkipSerialization within the filtered results due to wp_should_skip_block_supports_serialization in core only checking __experimentalSkipSerialization. It will have to stick around in the Gutenberg filter until 6.8 is the minimum supported version.

Next Steps

• Update uses of __experimentalSkipSerialization and __experimentalDefaultControls within Gutenberg's block supports
• Clean up and performance checks

Future follow-ups

• Updating core blocks within block library to use the stabilized keys.

Testing Instructions

Warning: This is likely going to need considerable testing!

1. Add a range of blocks to a post that use multiple types of block supports e.g. border, color, typography etc.
2. Check that all styles for these blocks display correctly when adjusted
3. Make sure that the block has appropriate controls available within Global Styles and the block inspector
4. Modify the block.json config for all the blocks to use varying combinations of experimental and stable flags.
5. Repeat steps 2 & 3 to ensure the newly modified config is reflected and styling continues to work as before
6. Add a filter to your theme that filters the block type arg in different ways and repeat the earlier checks again
7. Add multiple filters that would switch things up at each application of a filter.
8. Confirm the end result of config stabilizations and merges are as expected.

Screenshots or screencast

There should be no visual differences in blocks between this PR and trunk. Any found are regressions.