Updates the Global Styles endpoint to expose the `'edit_css'` capability via action links.
References:
* [https://github.com/WordPress/gutenberg/pull/46815 Gutenberg PR 46815] Part of an effort to hide custom CSS setting for users without `'edit_css'` capability.
Follow-up to [52342], [52051].
Props mamaduka, dsas, glendaviesnz, mmtr86, talldanwp, timothyblynjacobs.
Fixes#57526.
git-svn-id: https://develop.svn.wordpress.org/trunk@55177 602fd350-edb4-49c9-b593-d223f7449a82