Add: Template types to the patterns API.

Backports https://github.com/WordPress/gutenberg/pull/45814 into the core.
This commit adds a new templateType property to the patterns registration API.
This property allows a pattern to specify which template it makes sense on, e.g.: 404, single-post, single-product, category.

Props youknowriad, ntsekouras, 
spacedmonkey.

git-svn-id: https://develop.svn.wordpress.org/trunk@55168 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/block-patterns.php

@@ -302,6 +302,7 @@ function _register_remote_theme_patterns() {
  *   - Keywords         (comma-separated values)
  *   - Block Types      (comma-separated values)
  *   - Post Types       (comma-separated values)
+ *   - Template Types   (comma-separated values)
  *   - Inserter         (yes/no)
  *
  * @since 6.0.0
@@ -318,6 +319,7 @@ function _register_theme_block_patterns() {
 		'blockTypes'    => 'Block Types',
 		'postTypes'     => 'Post Types',
 		'inserter'      => 'Inserter',
+		'templateTypes' => 'Template Types',
 	);
 
 	/*
@@ -388,7 +390,7 @@ function _register_theme_block_patterns() {
 					}
 
 					// For properties of type array, parse data as comma-separated.
-					foreach ( array( 'categories', 'keywords', 'blockTypes', 'postTypes' ) as $property ) {
+					foreach ( array( 'categories', 'keywords', 'blockTypes', 'postTypes', 'templateTypes' ) as $property ) {
 						if ( ! empty( $pattern_data[ $property ] ) ) {
 							$pattern_data[ $property ] = array_filter(
 								preg_split(