Editor: Backport foundation for Layout block support refactor (part 1).
Backports the following changes from the Gutenberg repository:
- [WordPress/gutenberg/40875 gutenberg/40875] Layout: Use semantic classnames, centralize layout definitions, reduce duplication, and fix blockGap in theme.json
- [WordPress/gutenberg/42544 gutenberg/42544] Layout: Add a disable-layout-styles theme supports flag to opt out of all layout styles gutenberg/42544
- [WordPress/gutenberg/42087 gutenberg/42087] Theme.json: Add block support feature level selectors for blocks gutenberg/42087
- [WordPress/gutenberg/43792 gutenberg/43792] Global Styles: Split root layout rules into a different function gutenberg/43792
- [WordPress/gutenberg/42544 gutenberg/42544] Layout: Add a disable-layout-styles theme supports flag to opt out of all layout styles gutenberg/42544
- [WordPress/gutenberg/42665 gutenberg/42665] Layout: Reduce specificity of fallback blockGap styles gutenberg/42665
- [WordPress/gutenberg/42085 gutenberg/42085] Core CSS support for root padding and alignfull blocks gutenberg/42085
Notes:
- It doesn't entirely port over PR 40875 — the remaining PHP changes for that PR will be explored in a separate PR targeting
layout.php.
- [54159] was reverted in [54160] due to PHPUnit test failures for tests added by the commit. Later, tests passed when applied on top of
trunk. There were various outages today of upstream wp-env dependencies, which likely were the root cause of the earlier failures. For historical tracking and to make sure, recommitting [54159] but instead on top of current trunk. See PR 3205 for more details.
- Giving additional props for those who did a deep dive investigation into the failed tests.
Follow-up to [54160], [54159].
Props andrewserong, aaronrobertshaw, isabel_brison, bernhard-reiter, hellofromTonya.
See #56467.