FEATURE: Add an emoji deny list site setting (#20929)

This feature will allow sites to define which emoji are not allowed. Emoji in this list should be excluded from the set we show in the core emoji picker used in the composer for posts when emoji are enabled. And they should not be allowed to be chosen to be added to messages or as reactions in chat.

This feature prevents denied emoji from appearing in the following scenarios:
- topic title and page title
- private messages (topic title and body)
- inserting emojis into a chat
- reacting to chat messages
- using the emoji picker (composer, user status etc)
- using search within emoji picker

It also takes into account the various ways that emojis can be accessed, such as:
- emoji autocomplete suggestions
- emoji favourites (auto populates when adding to emoji deny list for example)
- emoji inline translations
- emoji skintones (ie. for certain hand gestures)

spec/system/page_objects/components/composer.rb

@@ -4,6 +4,7 @@ module PageObjects
   module Components
     class Composer < PageObjects::Components::Base
       COMPOSER_ID = "#reply-control"
+      AUTOCOMPLETE_MENU = ".autocomplete.ac-emoji"
 
       def opened?
         page.has_css?("#{COMPOSER_ID}.open")
@@ -14,6 +15,11 @@ module PageObjects
         self
       end
 
+      def click_toolbar_button(number)
+        find(".d-editor-button-bar button:nth-child(#{number})").click
+        self
+      end
+
       def fill_title(title)
         find("#{COMPOSER_ID} #reply-title").fill_in(with: title)
         self
@@ -54,6 +60,26 @@ module PageObjects
         find("#{COMPOSER_ID} .btn-primary .d-button-label")
       end
 
+      def emoji_picker
+        find("#{COMPOSER_ID} .emoji-picker")
+      end
+
+      def emoji_autocomplete
+        find(AUTOCOMPLETE_MENU)
+      end
+
+      def has_emoji_autocomplete?
+        has_css?(AUTOCOMPLETE_MENU)
+      end
+
+      def has_emoji_suggestion?(emoji)
+        has_css?("#{AUTOCOMPLETE_MENU} .emoji-shortname", text: emoji)
+      end
+
+      def has_emoji_preview?(emoji)
+        page.has_css?(".d-editor-preview .emoji[title=':#{emoji}:']")
+      end
+
       def composer_input
         find("#{COMPOSER_ID} .d-editor .d-editor-input")
       end