Editor: Backport wp_theme_element_class_name() alias.

This changeset backports the `wp_theme_element_class_name()` alias for the "internal" `WP_Theme_JSON::get_element_class_name()` function.

This is a backport of [WordPress/gutenberg#44099 gutenberg/PR44099].

Note: this changeset doesn't replace calls to `WP_Theme_JSON::get_element_class_name` in the tests, since those are specifically for the `WP_Theme_JSON` class.

Props bernhard-reiter, cbravobernal, costdev.
See #56467.


git-svn-id: https://develop.svn.wordpress.org/trunk@54174 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/theme.php

@@ -4210,6 +4210,21 @@ function wp_is_block_theme() {
 	return wp_get_theme()->is_block_theme();
 }
 
+/**
+ * Given an element name, returns a class name.
+ *
+ * Alias of WP_Theme_JSON::get_element_class_name.
+ *
+ * @since 6.1.0
+ *
+ * @param string $element The name of the element.
+ *
+ * @return string The name of the class.
+ */
+function wp_theme_get_element_class_name( $element ) {
+	return WP_Theme_JSON::get_element_class_name( $element );
+}
+
 /**
  * Adds default theme supports for block themes when the 'setup_theme' action fires.
  *