FEATURE: Add modal for editing tags in navigation menu (#22214)

What does this change do?

This change is a first pass for adding a modal used to edit tags that appears in
the navigation menu. As the feature is being worked on in phases, it is
currently hidden behind the `new_edit_sidebar_categories_tags_interface_groups` site setting.

The following features will be worked on in future commits:

1. Input filter to filter through the tgas
2. Button to reset tag selection to default navigation menu tags site
   settings
3. Button to deselect all current selection

spec/system/page_objects/components/sidebar.rb

@@ -31,6 +31,14 @@ module PageObjects
         PageObjects::Modals::SidebarEditCategories.new
       end
 
+      def click_edit_tags_button
+        within(".sidebar-section[data-section-name='tags']") do
+          click_button(class: "sidebar-section-header-button", visible: false)
+        end
+
+        PageObjects::Modals::SidebarEditTags.new
+      end
+
       def edit_custom_section(name)
         find(".sidebar-section[data-section-name='#{name.parameterize}']").hover
 
@@ -71,6 +79,10 @@ module PageObjects
         has_section?("Categories")
       end
 
+      def has_tags_section?
+        has_section?("Tags")
+      end
+
       def has_no_section?(name)
         find(SIDEBAR_WRAPPER_SELECTOR).has_no_button?(name)
       end