FIX: prevents setPanel to also set separated mode (#23227)

This could happen after you had already change the separation mode and would cause unexpected bugs.

This PR also adds more tests around using switch buttons with chat.

spec/system/page_objects/components/navigation_menu/base.rb

@@ -34,6 +34,10 @@ module PageObjects
           find(".sidebar__panel-switch-button[data-key='chat']").click
         end
 
+        def switch_to_main
+          find(".sidebar__panel-switch-button[data-key='main']").click
+        end
+
         def has_no_section?(name)
           has_no_css?(".sidebar-sections [data-section-name='#{name.parameterize}']")
         end