Fixes a bug of invalid CSS value when applying block spacing to a block as reported in [https://github.com/WordPress/gutenberg/issues/44435 Gutenberg issue 44435].
Adds logic to convert preset values (i.e. `$gap_value`) into valid CSS custom properties for the flow ('default') layout type. See the original fix in [https://github.com/WordPress/wordpress-develop/pull/3324 Gutenberg PR 3324].
Also adds a test dataset that fails before the bugfix and passes after the bugix.
Follow-up to [54274].
Props ndiego, isabel_brison, ramonopoly, andrewserong, hellofromTonya.
See #56467.
git-svn-id: https://develop.svn.wordpress.org/trunk@54311 602fd350-edb4-49c9-b593-d223f7449a82
This commit merges the remaining changes from [https://github.com/WordPress/gutenberg/pull/40875 Gutenberg PR 40875]. It's Part 2 (see [54162] for Part 1) of a layout improvement initiative and targets `wp_get_layout_style()` in `layout.php`.
Context:
The overall initiative is to improve layout block support:
>to use centralised layout definitions, output base layout styles from global styles, introduce a layout type semantic classname, reduce duplication of container class and style tag output, and fix blockGap at the block level in global styles.
Changes include:
* Adding an optional parameter `$block_spacing` to `wp_get_layout_style()` for setting a custom spacing on the block.
* Adding handle for the block spacing.
* Using the style engine to to enqueue and render layout styles via `wp_style_engine_get_stylesheet_from_css_rules()`.
* Introduces a new test file for `wp_get_layout_style()`.
Follow-up to [54162], [54160], [54159], [53421], [52380], [53085], [52069].
Props andrewserong, isabel_brison, costdev, hellofromTonya.
See #56467.
git-svn-id: https://develop.svn.wordpress.org/trunk@54274 602fd350-edb4-49c9-b593-d223f7449a82
