Media: Fix input position shift during admin search.

Avoid layout element shift by setting position attributes on `.media-bg-overlay` in all viewports, avoiding redraw of flex layout.

Props abduremon, mohamedahamed, wildworks, khokansardar, darshitrajyaguru97, joedolson.
Fixes #65296.

git-svn-id: https://develop.svn.wordpress.org/trunk@62469 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-includes/css/media-views.css

@@ -1834,6 +1834,10 @@ select#media-attachment-date-filters {
 	visibility: visible;
 }
 
+.media-bg-overlay {
+	position: absolute;
+}
+
 /**
  * Attachment Details
  */
@@ -2901,7 +2905,6 @@ select#media-attachment-date-filters {
 		width: 100%;
 		height: 100%;
 		display: none;
-		position: absolute;
 		left: 0;
 		right: 0;
 		top: 0;