Use Codex styles for buttons in language overlay (attempt 2)

* Replace all instances of mw-ui markup with Codex markup
* Use codex-search-styles
* Where codex-search-styles is not installed (e.g. 1.39)
register an alias which points to @wikimedia/codex as that is
available.

Bug: T340255
Bug: T340257
Change-Id: I4f3ddfb68ea6c033ee7a49729187f4ddbc8abe5c

resources/js/ext.uls.compactlinks.js

@@ -190,7 +190,7 @@
 			this.compactList[ language ].parentNode.style.display = '';
 		}
 
-		mw.loader.using( 'mediawiki.ui.button' ).then( function () {
+		mw.loader.using( '@wikimedia/codex' ).then( function () {
 			this.addTrigger();
 		}.bind( this ) );
 
@@ -330,7 +330,7 @@
 	CompactInterlanguageList.prototype.addTrigger = function () {
 		var trigger = document.createElement( 'button' );
 		// TODO: Should we have a different class name where the CLS styles are attached?
-		trigger.className = 'mw-interlanguage-selector mw-ui-button';
+		trigger.className = 'mw-interlanguage-selector cdx-button';
 		trigger.title = mw.message( 'ext-uls-compact-link-info' ).plain();
 		// Use text() because the message needs {{PLURAL:}}
 		trigger.textContent = mw.message(