Show tiles for members we're trying to connect to

This should help give more context on what's going wrong in
splitbrain scenarios.

If users leave calls uncleanly, their tile will remain in until
their member event times out, which will be an hour from when they
joined the call. See https://github.com/vector-im/element-call/issues/639.

Part of https://github.com/vector-im/element-call/issues/616

src/video-grid/VideoGrid.tsx

@@ -23,7 +23,7 @@ import { ReactDOMAttributes } from "@use-gesture/react/dist/declarations/src/typ
 
 import styles from "./VideoGrid.module.css";
 import { Layout } from "../room/GridLayoutMenu";
-import { Participant } from "../room/InCallView";
+import { TileDescriptor } from "../room/InCallView";
 
 interface TilePosition {
   x: number;
@@ -36,7 +36,7 @@ interface TilePosition {
 interface Tile {
   key: Key;
   order: number;
-  item: Participant;
+  item: TileDescriptor;
   remove: boolean;
   focused: boolean;
   presenter: boolean;
@@ -693,12 +693,12 @@ interface ChildrenProperties extends ReactDOMAttributes {
   };
   width: number;
   height: number;
-  item: Participant;
+  item: TileDescriptor;
   [index: string]: unknown;
 }
 
 interface VideoGridProps {
-  items: Participant[];
+  items: TileDescriptor[];
   layout: Layout;
   disableAnimations?: boolean;
   children: (props: ChildrenProperties) => React.ReactNode;