Editor: Skip file_exist check for core blocks.

In `register_block_type_from_metadata` function, skip calling `file_exists` on core blocks. Core blocks are part of the codebase and will never not exist. Not calling this function is better for performance, as the file lookup can be expensive. 

Props spacedmonkey, joemcgill.
Fixes #58385.

git-svn-id: https://develop.svn.wordpress.org/trunk@55910 602fd350-edb4-49c9-b593-d223f7449a82

Author: spacedmonkey

src/wp-includes/blocks.php

@@ -326,13 +326,15 @@ function register_block_type_from_metadata( $file_or_folder, $args = array() ) {
 		trailingslashit( $file_or_folder ) . 'block.json' :
 		$file_or_folder;
 
-	if ( ! file_exists( $metadata_file ) ) {
+	$is_core_block = str_starts_with( $file_or_folder, ABSPATH . WPINC );
+
+	if ( ! $is_core_block && ! file_exists( $metadata_file ) ) {
 		return false;
 	}
 
 	// Try to get metadata from the static cache for core blocks.
 	$metadata = false;
-	if ( str_starts_with( $file_or_folder, ABSPATH . WPINC ) ) {
+	if ( $is_core_block ) {
 		$core_block_name = str_replace( ABSPATH . WPINC . '/blocks/', '', $file_or_folder );
 		if ( ! empty( $core_blocks_meta[ $core_block_name ] ) ) {
 			$metadata = $core_blocks_meta[ $core_block_name ];