Add new textAlign block support

[t-hamano]

Trac ticket: https://core.trac.wordpress.org/ticket/61256

This PR backports the following three PHP changes in Gutenberg PR:

• Try: Add new textAlign block support gutenberg#59531
• Fix: Enable Text Align UI to be controlled correctly with theme.json gutenberg#61182
• Global Styles: Add block-level Text Alignment UI gutenberg#61717

This PR enables textAlign block support on the server-side.

Testing Instructions

Currently, there are no blocks that support textAlign, so please add the following changes to your theme's functions.php. This enables textAlign support in the Archive block.

function custom_block_type_metadata_settings( $settings, $metadata ) {
	if ( $settings['name'] === 'core/archives' ) {
		$settings['supports']['typography']['textAlign'] = true;
	}
	return $settings;
}
add_filter( 'block_type_metadata_settings', 'custom_block_type_metadata_settings', 10, 2 );

Next, switch the post editor to the code editor and paste the code below.

<!-- wp:archives {"style":{"typography":{"textAlign":"center"}}} /-->

Save the post and check it on the front end. The block should be given the has-text-align-center class and the text should be centered left and right.

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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Core Committers: Use this line as a base for the props when committing in SVN:

Props wildworks, ellatrix.

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Test this pull request with WordPress Playground.

[ellatrix]

@t-hamano Could you rebase this?

[t-hamano]

Could you rebase this?

Done.

[ellatrix]

I saw the test result adds a style here

:root :where(.wp-block-media-text){text-align: center;}

But above I see that we're adding classes instead of style properties. So is this normal?

[ellatrix]

I see, these are global styles.

[ellatrix]

Works, changes make sense.