Accessibility: Improve the Menus post type meta boxes pagination links.

- adds hidden text to the pagination links
- slightly increases the links clickable area
- fixes a JS error when clicking on the current page number
- avoids to generate nested `<div>` elements at each click 

Props xavortm, cwpnolen, afercia.

Fixes #35577.


git-svn-id: https://develop.svn.wordpress.org/trunk@38981 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/nav-menus.css

@@ -693,10 +693,19 @@ body.menu-max-depth-11 { min-width: 1280px !important; }
 }
 
 .add-menu-item-pagelinks {
-	margin: .5em auto;
+	margin: .5em -10px;
 	text-align: center;
 }
 
+.add-menu-item-pagelinks .page-numbers {
+	display: inline-block;
+	min-width: 20px;
+}
+
+.add-menu-item-pagelinks .page-numbers.dots {
+	min-width: 0;
+}
+
 .link-to-original {
 	display: block;
 	margin: 0 0 15px;