Related to:

• Stabilize Typography Block Supports Keys #63001 and
• Tracking: Addressing Design Tooling Consistency #43241

Borrowing from the format of #63001, this issue outlines the tasks needed to stabilize the __experimentalBorder support. Doing so will make it easier for third-party extenders to confidently build custom blocks that provide border support and modify existing blocks with this support.

Note that in order to provide backward compatibility for block plugins out in the wild, fallback support for the existing __experimental prefix should be provided.

Stabilize the following border block support and associated properties:

• __experimentalBorder → border
• __experimentalBorder.color → border.color
• __experimentalBorder.radius → border.radius
• __experimentalBorder.style → border.style
• __experimentalBorder.width → border.width

Tasks

• Update PHP block support code in lib/block-supports/border.php to use the non __experimental prefix
• Update the JS implementations of the border block supports to point to the non __experimental prefix
• Update the block.json schema to support the non __experimental prefix
• Update the core blocks' block.json files to use the non __experimental prefixes
• Update the supports documentation to include a section for border support.
• Update the block.json schema to remove the __experimental prefix. Note that the code in WordPress should still support the __experimental prefix, but at this stage, the experimental prefix will be treated as deprecated.

The PR for this stabilization effort should follow the approach used to stabilize the typography supports in #63401.