Block Supports: Add width support to dimensions block supports

[aaronrobertshaw]

This ticket tracks the backport of PHP files for the following Gutenberg updates:

​https://github.com/WordPress/gutenberg/pull/71905

These updates include the PHP changes to add width block supports.

New dimensions block supports are being added to support new blocks such as the proposed Icon block. See ​https://github.com/WordPress/gutenberg/pull/71227 for further context.

Trac ticket: https://core.trac.wordpress.org/ticket/64200

This PR brings the changes from the following Gutenberg PRs to core:

​https://github.com/WordPress/gutenberg/pull/71905

### Description

Adds a new dimensions.width block support to facilitate the creation of new blocks such as the Icon block.

See: ​https://github.com/WordPress/gutenberg/pull/71227

### Testing

1. Adopt width block support for a dynamic block e.g. Cover via its block.json file
2. Add a width value for the chosen test block in your theme.json file
3. Create a post with the test block type
4. Confirm the global style is applied to your test block

[audrasjb]

As per today's 7.0 bug scrub:
This is a Gutenberg merge ticket and there's a PR, but it's still a draft for now. Pinging @aaronrobertshaw for a status update.

[aaronrobertshaw]

Thanks for the ping. There were some further follow ups to the block support in Gutenberg. I'll update this PR as soon as possible and get this backport reviewed.

[ramonopoly]

In 61619:

Block Supports: Add width to dimensions supports

This PR introduces dimensions.width to the list of available block supports.

This block support enables, in the future, the removal of the custom width and height controls in blocks such as Button, Column and many others in favor of customizations via block supports.

Props aaronrobertshaw, andrewserong, ramonopoly, welcher, mamaduka, wildworks, youknowriad, isabel_brison.

Fixes #64200.

Committed in r61619 and ​https://github.com/WordPress/wordpress-develop/commit/5ca0471d35aa13ad95d4843cc6a3036c71ab3387

[audrasjb]

This is worth mentioning in the Field Guide.
Also adding needs-dev-note just in case we can mention it in a more general note.