Themes: Allow use of sidebar submenus when theme details open.

Increase the z-index of sidebar submenus in the theme browser screens so that submenus are not placed behind the theme details overlay. Also set a min-height to ensure the overlay covers the entire screen if content is short.

Props codexdemon, amolebonde, yahil, girishpanchal, chintanmachhi207, mp518, janak007, worldweb, ralessio, sabernhardt, boogah, mikinc860, adamsilverstein, subrataemfluence, huzaifaalmesbah, lakshmananphp, amin7, imranhasanraaz, mdibrahimk48. 
Fixes #41155.
Built from https://develop.svn.wordpress.org/trunk@59821


git-svn-id: http://core.svn.wordpress.org/trunk@59163 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/themes-rtl.css

@@ -12,6 +12,10 @@
 	overflow-y: scroll;
 }
 
+.themes-php #adminmenuwrap {
+	z-index: 10001; /* above Theme Overlay */
+}
+
 body.js .theme-browser.search-loading {
 	display: none;
 }
@@ -373,6 +377,7 @@ body.js .theme-browser.search-loading {
 	background: #f0f0f1;
 	background: rgba(240, 240, 241, 0.9);
 	z-index: 10000; /* Over WP Pointers. */
+	min-height: calc(100vh - var(--wp-admin--admin-bar--height, 32px));
 }
 
 .theme-overlay .theme-header {

wp-admin/css/themes.css

@@ -11,6 +11,10 @@
 	overflow-y: scroll;
 }
 
+.themes-php #adminmenuwrap {
+	z-index: 10001; /* above Theme Overlay */
+}
+
 body.js .theme-browser.search-loading {
 	display: none;
 }
@@ -372,6 +376,7 @@ body.js .theme-browser.search-loading {
 	background: #f0f0f1;
 	background: rgba(240, 240, 241, 0.9);
 	z-index: 10000; /* Over WP Pointers. */
+	min-height: calc(100vh - var(--wp-admin--admin-bar--height, 32px));
 }
 
 .theme-overlay .theme-header {

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59820';
+$wp_version = '6.8-alpha-59821';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.