Introduce dimensions.minHeight block support

[andrewserong]

In the Gutenberg plugin, a minimum height block support feature was added, with support for both Group and Post Content blocks. It would be good to backport this feature for the WP 6.2 release. While the feature is spread across JS and PHP code, it should be possible to land most of the PHP implementation in advance of the JS packages update for core.

The original feature landed in Gutenberg across the following PRs:

• ​https://github.com/WordPress/gutenberg/pull/45300
• ​https://github.com/WordPress/gutenberg/pull/45334

This PR backports the minimum height block support feature's PHP changes from Gutenberg. Those changes were originally merged in the following PRs:

• ​https://github.com/WordPress/gutenberg/pull/45334 and
• ​https://github.com/WordPress/gutenberg/pull/45300

The opting-in of the block support for particular blocks, and UI support will land separately as part of the main JS package update for 6.2 — hopefully, this PHP change should be able to safely land in isolation.

Trac ticket: https://core.trac.wordpress.org/ticket/57582

Status: Currently reviewing and testing for commit consideration.

[hellofromTonya]

Self-assigning for review and commit.

[hellofromTonya]

​PR 3940:

• Confirmed the PHP changes from the GB PRs are here ✅
• Confirmed there's no BC issue for the removal of experimentalDimensions setting ✅
• Reviewed for coding standards ✅
• Tests are okay ✅
• It's been tested ✅

Marking for commit.

[hellofromTonya]

In 55175:

Editor: Introduce minimum height dimensions block support.

This changeset adds the new dimension feature's PHP code for supporting minimum height in the block editor inspector and in global styles. Minimum height is quite useful for defining the minimum vertical dimensions of a block, while allowing it to expand beyond that size.

In this changeset:

• Adds support in theme.json.
• Adds support in the style engine.
• Adds support in wp_apply_dimensions_support().
• Renames the setting from '__experimentalDimensions' to dimensions in wp_register_dimensions_support().
• Adds PHPUnit tests.

Is renaming '__experimentalDimensions' a backwards-compatibility (BC) break?

Though the setting has been in the code since 5.9.0, it was never wired to anything, ie it did not expose any controls or styles. Notice in wp_register_dimensions_support() and wp_apply_dimensions_support() prior to this changeset, there are inline comments as placeholders for height and width support, but no code.

If a developer opted in to use it, it had no effect.

A search in wp.org's plugin and themes repo showed no instances of this experimental setting.

Given there was no functionality attached to it (until this changeset), no change in behavior or effect from removing it, and no usage found in the plugins and themes repository, it does appear to be a BC break.

References:

• ​Gutenberg PR 45300
• ​Gutenberg PR 45334

Follow-up to [53076], [52069].

Props andrewserong, aaronrobertshaw , costdev, hellofromTonya, isabel_brison, joen, paaljoachim, mukesh27, ntsekouras, oandregal, ramonopoly.
Fixes #57582.

Committed via https://core.trac.wordpress.org/changeset/55175.

Wonderful, thank you for landing this one, and for the extra discussion, I learn more with each of these PRs 🙂