Editor: Add textColumn block support to appearance tools opt-ins.

This changeset adds `textColumn` block support to appearance tools opt-ins.
Backports Gutenberg PR 74656: WordPress/gutenberg#74656

Props scruffian, wildworks.
Fixes #64530


git-svn-id: https://develop.svn.wordpress.org/trunk@61570 602fd350-edb4-49c9-b593-d223f7449a82

Author: audrasjb

src/wp-includes/class-wp-theme-json.php

@@ -744,6 +744,7 @@ public static function get_element_class_name( $element ) {
 		array( 'spacing', 'margin' ),
 		array( 'spacing', 'padding' ),
 		array( 'typography', 'lineHeight' ),
+		array( 'typography', 'textColumns' ),
 	);
 
 	/**

tests/phpunit/tests/theme/wpThemeJson.php

@@ -291,13 +291,14 @@ public function test_get_settings_appearance_true_opts_in() {
 				'padding'  => true,
 			),
 			'typography' => array(
-				'lineHeight' => true,
+				'lineHeight'  => true,
+				'textColumns' => true,
 			),
 			'blocks'     => array(
 				'core/paragraph' => array(
 					'typography' => array(
-						'lineHeight' => false,
-					),
+						'lineHeight'  => false,
+						'textColumns' => true,					),
 				),
 				'core/group'     => array(
 					'background' => array(