WordPress default presets aren't loaded for all themes

[oandregal]

The default preset styles of WordPress (font sizes, colors, gradients) are now provided via the global stylesheet to avoid duplication of styles. This stylesheet can be found in the front-end with the name global-styles-inline-css.

The default presets are important to support old content that may use them and also patterns, that can use cross-theme styles.

Track ticket https://core.trac.wordpress.org/ticket/54781

For themes without theme.json support, we only enqueue the default styles provided by WordPress, such as the preset classes
(font sizes, colors, gradients). These classes should be always present as they may be used by old content and patterns.

For themes with theme.json support, we also enqueue the theme styles.

## More context

In WordPress 5.8 the preset classes (font sizes, colors, gradients) were provided via a CSS stylesheet that we enqueued to all themes plus the global stylesheet for the themes that supported theme.json. To avoid this duplication, in WordPress 5.9 the preset classes were removed from the common stylesheet (see ​https://github.com/WordPress/gutenberg/pull/35182 and ​https://github.com/WordPress/gutenberg/pull/34510) and are now provided by the global stylesheet, which is enabled to all themes as of ​https://github.com/WordPress/gutenberg/pull/34334

Related ​devnote, see "Changes to the global stylesheet" section.

## How to test

• Load the TwentyTwenty theme.
• Go to the front end and verify that there's a stylesheet called global-styles-inline-css.

[jorgefilipecosta]

In 52547:

Fix: WordPress default presets aren't loaded for all themes.

The default preset styles of WordPress (font sizes, colors, gradients) are now provided via the global stylesheet to avoid duplication of styles. This stylesheet can be found in the front-end with the name global-styles-inline-css.
The default presets are important to support old content that may use them and also patterns, that can use cross-theme styles.

Props oandregal.
Fixes #54781.

Related issue at https://core.trac.wordpress.org/ticket/54782

I have a fix for TwentyTwenty at ​https://github.com/WordPress/wordpress-develop/pull/2130 TwentyNineteen and TwentyTwentyone still need a patch.

[jorgefilipecosta]

In 52548:

Fix: WordPress default presets aren't loaded for all themes.

The default preset styles of WordPress (font sizes, colors, gradients) are now provided via the global stylesheet to avoid duplication of styles. This stylesheet can be found in the front-end with the name global-styles-inline-css.
The default presets are important to support old content that may use them and also patterns, that can use cross-theme styles.

Props oandregal.
Merges [52547] to the 5.9 branch.
Fixes #54781.

[jorgefilipecosta]

Backported to the 5.9 branch.

Merged as of ​https://github.com/WordPress/wordpress-develop/commit/16e0165cf00d87935a0ece5d75053572160b6d53

Thanks @oandregal!