dash: Resolve padding and alignment issues with dash items

- revert a change to y-expand on dash items
- clean up the manual padding on dash items in stylesheet
- fix an issue with the running dot being misaligned

Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7322
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3119>

js/ui/dash.js

@@ -153,7 +153,7 @@ class DashItemContainer extends St.Widget {
         this.destroy_all_children();
 
         this.child = actor;
-        this.child.y_expand = false;
+        this.child.y_expand = true;
         this.add_child(this.child);
     }