Block Supports: Add width to dimensions supports

[aaronrobertshaw]

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

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

WordPress/gutenberg#71905

Description

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

See: WordPress/gutenberg#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

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

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