Add data models for the new call layouts

This is a start at implementing the call layouts from the new designs. I've added data types to model the contents of each possible layout, and begun implementing the business logic to produce these layouts in the call view model.

src/video-grid/VideoTile.tsx

@@ -58,10 +58,10 @@ import { Avatar } from "../Avatar";
 import styles from "./VideoTile.module.css";
 import { useReactiveState } from "../useReactiveState";
 import {
-  ScreenShareTileViewModel,
-  TileViewModel,
-  UserMediaTileViewModel,
-} from "../state/TileViewModel";
+  ScreenShareViewModel,
+  MediaViewModel,
+  UserMediaViewModel,
+} from "../state/MediaViewModel";
 import { subscribe } from "../state/subscribe";
 import { useMergedRefs } from "../useMergedRefs";
 import { Slider } from "../Slider";
@@ -170,7 +170,7 @@ const Tile = forwardRef<HTMLDivElement, TileProps>(
 Tile.displayName = "Tile";
 
 interface UserMediaTileProps {
-  vm: UserMediaTileViewModel;
+  vm: UserMediaViewModel;
   className?: string;
   style?: ComponentProps<typeof animated.div>["style"];
   targetWidth: number;
@@ -329,7 +329,7 @@ const UserMediaTile = subscribe<UserMediaTileProps, HTMLDivElement>(
 UserMediaTile.displayName = "UserMediaTile";
 
 interface ScreenShareTileProps {
-  vm: ScreenShareTileViewModel;
+  vm: ScreenShareViewModel;
   className?: string;
   style?: ComponentProps<typeof animated.div>["style"];
   targetWidth: number;
@@ -403,7 +403,7 @@ const ScreenShareTile = subscribe<ScreenShareTileProps, HTMLDivElement>(
 ScreenShareTile.displayName = "ScreenShareTile";
 
 interface Props {
-  vm: TileViewModel;
+  vm: MediaViewModel;
   maximised: boolean;
   fullscreen: boolean;
   onToggleFullscreen: (itemId: string) => void;
@@ -455,7 +455,7 @@ export const VideoTile = forwardRef<HTMLDivElement, Props>(
       ? t("video_tile.sfu_participant_local")
       : displayName;
 
-    if (vm instanceof UserMediaTileViewModel) {
+    if (vm instanceof UserMediaViewModel) {
       return (
         <UserMediaTile
           ref={ref}