refactor: Use more robust and performant way to detect single emoji messages

lib/pages/chat/chat.dart

@@ -104,6 +104,8 @@ class ChatController extends State<ChatPageWithRoom>
 
   String? activeThreadId;
 
+  late final Set<String> bigEmojis;
+
   late final String readMarkerEventId;
 
   String get roomId => widget.room.id;
@@ -360,6 +362,14 @@ class ChatController extends State<ChatPageWithRoom>
       AppSettings.displayChatDetailsColumn.value,
     );
 
+    bigEmojis = defaultEmojiSet.fold(
+      <String>{},
+      (emojis, category) => {
+        ...emojis,
+        ...(category.emoji.map((emoji) => emoji.emoji)),
+      },
+    );
+
     sendingClient = Matrix.of(context).client;
     final lastEventThreadId =
         room.lastEvent?.relationshipType == RelationshipTypes.thread