ULS Frontend: Save preferences only for named users

Add a new method isNamed in ext.uls.common to use the isNamed
method if available else use the isAnon method as usual.

mw.user.isNamed was added in MW 1.40

Bug: T337780
Change-Id: I747c042a95e8edc793a2265a15ed6ba8ae9f1997

resources/js/ext.uls.displaysettings.js

@@ -188,7 +188,7 @@
 				lang, i, language, $button, autonym;
 
 			// Don't let anonymous users change interface language
-			if ( !anonsAllowed && mw.user.isAnon() ) {
+			if ( !anonsAllowed && !mw.uls.isNamed() ) {
 				$loginCta = $( '<p>' )
 					.attr( 'id', 'uls-display-settings-anon-log-in-cta' );
 				autonym = $.uls.data.getAutonym( this.contentLanguage );