UX: multiple drafts menu improvements (#31195)

This change includes the following updates:

- Rename view all to view all drafts
- Remove view all link from drop-down when all drafts are displayed in
the menu
- Different icon for draft topics and PMs (adds envelope for PMs)
- Disable drop-down when New Topic button is disabled (private
categories etc)
- Improve drafts drop-down loading (no longer disables the trigger btn
on click)

spec/system/page_objects/components/drafts_menu.rb

@@ -13,6 +13,10 @@ module PageObjects
         has_no_css?(MENU_SELECTOR + "-trigger")
       end
 
+      def disabled?
+        find(MENU_SELECTOR + "-trigger")["disabled"]
+      end
+
       def open?
         has_css?(MENU_SELECTOR + "-content")
       end
@@ -21,6 +25,14 @@ module PageObjects
         has_no_css?(MENU_SELECTOR + "-content")
       end
 
+      def has_view_all_link?
+        has_css?(MENU_SELECTOR + "-content .view-all-drafts")
+      end
+
+      def has_no_view_all_link?
+        has_no_css?(MENU_SELECTOR + "-content .view-all-drafts")
+      end
+
       def open
         find(MENU_SELECTOR + "-trigger").click
       end