Adds shadow presets support in theme.json

[Mamaduka]

Adds shadow presets support via theme.json file for block and hybrid themes.

Covers following PRs:

• ​https://github.com/WordPress/gutenberg/pull/46813
• ​https://github.com/WordPress/gutenberg/pull/47272

Trac ticket: https://core.trac.wordpress.org/ticket/57559

Gutenberg PRs:

• ​https://github.com/WordPress/gutenberg/pull/46813
• ​https://github.com/WordPress/gutenberg/pull/47272

I just pushed the theme.json update for shadow presets. Based on the diff, this is the only change since WP 6.1, so I won't create a separate PR.

Cc @oandregal

I just pushed the theme.json update for shadow presets. Based on the diff, this is the only change since WP 6.1, so I won't create a separate PR.

:+1: Good call, those changes pertain to this feature as well.

Current reviewing. There are a few tweaks needed to the tests. And there's a merge conflict.

[hellofromTonya]

Self-assigning for review and commit.

Rebase this PR on top of wordpress-develop current trunk branch to resolve the merge conflict. Force pushed.

[hellofromTonya]

​PR 3915 is ready for commit.

• Confirmed both GB PRs are present in this PR ✅
• Changes are noted in @since 6.2.0 ✅
• Includes tests ✅
• Has a test report ✅

[hellofromTonya]

In 55176:

Themes: Add shadow presets support for theme.json.

Adds shadow presets support for theme.json within the WP_Theme_JSON by

• Adding it to presets metadata and valid settings.
• Defining the default shadow presets in Core's theme.json.

Includes PHPUnit tests.

References:

• ​Gutenberg PR 46813
• ​Gutenberg PR 47272

Follow-up to [54162], [52049], [50973].

Props madhudollu, mamaduka, oandregal, scruffian, hellofromTonya.
Fixes #57559.

Committed via https://core.trac.wordpress.org/changeset/55176.

[hellofromTonya]

In 55405:

Themes: Add 3 and update 2 shadow presets in theme.json.

Adds Deep, Outlined, and Crisp default shadow presets to Core's theme.json file.

Updates the Natural and Sharp 'shadow' styles.

These shadow presets are used to populate the Shadow tools in the Site Editor's Global Styles UI.

References:

• ​Gutenberg PR 46502

Follow-up to [55176].

Props franz00, madhudollu, ajlende, beafialho, costdev, dhrupo, fabiankaegy, hellofromTonya, jameskoster, joen, kellychoffman, mamaduka, mtias, oandregal, priethor, richtabor, scruffian.
Fixes #57708.
See #57559.