status/remote-access: Split out screen sharing indicator

The latest mockups move the screen sharing indicator into a
separate control, similar to the existing indicator for built-in
screen recordings.

As this removes the submenu and only keeps the top bar icon (for
external screen recordings), this will smooth the transition to
quick settings.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2391>

js/ui/sessionMode.js

@@ -94,7 +94,7 @@ const _modes = {
         panel: {
             left: ['activities', 'appMenu'],
             center: ['dateMenu'],
-            right: ['screenRecording', 'dwellClick', 'a11y', 'keyboard', 'aggregateMenu'],
+            right: ['screenRecording', 'screenSharing', 'dwellClick', 'a11y', 'keyboard', 'aggregateMenu'],
         },
     },
 };