General: Memoize the return value in `wp_get_wp_version()`.

Cache the unmodified `$wp_version` value as a static. This retains the current behaviour during the upgrade process `$wp_version` referencing the version of WordPress being upgraded from.

Follow up to [58848].

Props Cybr, debarghyabanerjee, mukesh27, costdev, SergeyBiryukov, TobiasBg, desrosj, azaozz.
Fixes #61782.

Built from https://develop.svn.wordpress.org/trunk@59192


git-svn-id: http://core.svn.wordpress.org/trunk@58587 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -8833,7 +8833,11 @@ function clean_dirsize_cache( $path ) {
  * @return string The current WordPress version.
  */
 function wp_get_wp_version() {
+	static $wp_version;
+
+	if ( ! isset( $wp_version ) ) {
 		require ABSPATH . WPINC . '/version.php';
+	}
 
 	return $wp_version;
 }

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-beta1-59191';
+$wp_version = '6.7-beta1-59192';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.