Release video rooms as a beta feature (#8431)

* Remove blank header from video room view frame

* Add a beta card for video rooms

* Rename the 'disclaimer' on beta cards to 'FAQ'

Because that's what the section actually gets used as

* Add beta pills to video room creation buttons

* Remove duplicate tooltips from face piles

* Add beta pill to headers of video rooms

* Factor RoomInfoLine out of SpaceRoomView

* Factor RoomPreviewCard out of SpaceRoomView

* Adapt RoomPreviewCard for video rooms

* "New video room" → "Video room"

* Add comment about unused cases in RoomPreviewCard

* Add types

* Clarify !important comments

* Add a reload warning

* Fix the reload warning being the wrong way around

* Fix lints

* Make widgets in video rooms mutable again to de-risk future upgrades

* Ensure that the video channel exists when mounting VideoRoomView

* Fix lint

* Iterate beta reload warning

src/components/views/rooms/RoomPreviewCard.tsx

@@ -35,6 +35,7 @@ import RoomTopic from "../elements/RoomTopic";
 import RoomFacePile from "../elements/RoomFacePile";
 import RoomAvatar from "../avatars/RoomAvatar";
 import MemberAvatar from "../avatars/MemberAvatar";
+import { BetaPill } from "../beta/BetaCard";
 import RoomInfoLine from "./RoomInfoLine";
 
 interface IProps {
@@ -151,6 +152,7 @@ const RoomPreviewCard: FC<IProps> = ({ room, onJoinButtonClicked, onRejectButton
         avatarRow = <>
             <RoomAvatar room={room} height={50} width={50} viewAvatarOnClick />
             <div className="mx_RoomPreviewCard_video" />
+            <BetaPill onClick={viewLabs} tooltipTitle={_t("Video rooms are a beta feature")} />
         </>;
     } else if (room.isSpaceRoom()) {
         avatarRow = <RoomAvatar room={room} height={80} width={80} viewAvatarOnClick />;