Add low priority avatar decoration to room tile (#30065)

* Add avatar decoration for low priority rooms

* Write tests

* Remove unnecesasry step in test

* Make the vm expose which decoration to render

* Fix jest test

* Fix broken e2e test

src/i18n/strings/en_EN.json

@@ -2047,6 +2047,7 @@
         "read_topic": "Click to read topic",
         "rejecting": "Rejecting invite…",
         "rejoin_button": "Re-join",
+        "room_is_low_priority": "This is a low priority room",
         "search": {
             "all_rooms_button": "Search all rooms",
             "placeholder": "Search messages…",