Stabilize the __experimentalDefaultControls block supports property

[ndiego]

Related to #43241.

The __experimentalDefaultControls property lets developers choose which settings are displayed by default in the Editor for each block support. This property is often used when creating custom blocks that utilize block supports or when customizing the Editor experience. Removing the __experimental prefix will make it easier for third-party developers to confidently use this property.

• __experimentalDefaultControls → defaultControls

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.

Tasks

This is a preliminary list based on the format of #63001, but it is likely incomplete.

• Update the JS implementations of the default controls to point to the non __experimental prefix, falling back to the __experimental prefix if available.
• 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 about default controls.
• 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.