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/context_menus/SpaceContextMenu.tsx

@@ -184,7 +184,9 @@ const SpaceContextMenu = ({ space, hideHeader, onFinished, ...props }: IProps) =
                     iconClassName="mx_SpacePanel_iconPlus"
                     label={_t("Video room")}
                     onClick={onNewVideoRoomClick}
-                />
+                >
+                    <BetaPill />
+                </IconizedContextMenuOption>
             }
             { canAddSubSpaces &&
                 <IconizedContextMenuOption