Compute the 'waiting for media' state less implicitly

On second glance, the way that we determined a media tile to be 'waiting for media' was too implicit for my taste. It would appear on a surface reading to depend on whether a participant was currently publishing any video. But in reality, the 'video' object was always defined as long as a LiveKit participant existed, so in reality it depended on just the participant. We should show this relationship more explicitly by moving the computation into the view model, where it can depend on the participant directly.

src/tile/MediaView.test.tsx

@@ -47,7 +47,6 @@ describe("MediaView", () => {
     video: trackReference,
     userId: "@alice:example.com",
     mxcAvatarUrl: undefined,
-    localParticipant: false,
     focusable: true,
   };
 
@@ -66,24 +65,13 @@ describe("MediaView", () => {
     });
   });
 
-  describe("with no participant", () => {
-    it("shows avatar for local user", () => {
-      render(
-        <MediaView {...baseProps} video={undefined} localParticipant={true} />,
-      );
+  describe("with no video", () => {
+    it("shows avatar", () => {
+      render(<MediaView {...baseProps} video={undefined} />);
       expect(
         screen.getByRole("img", { name: "@alice:example.com" }),
       ).toBeVisible();
-      expect(screen.queryAllByText("Waiting for media...").length).toBe(0);
-    });
-    it("shows avatar and label for remote user", () => {
-      render(
-        <MediaView {...baseProps} video={undefined} localParticipant={false} />,
-      );
-      expect(
-        screen.getByRole("img", { name: "@alice:example.com" }),
-      ).toBeVisible();
-      expect(screen.getByText("Waiting for media...")).toBeVisible();
+      expect(screen.queryByTestId("video")).toBe(null);
     });
   });
 
@@ -94,6 +82,22 @@ describe("MediaView", () => {
     });
   });
 
+  describe("waitingForMedia", () => {
+    test("defaults to false", () => {
+      render(<MediaView {...baseProps} />);
+      expect(screen.queryAllByText("Waiting for media...").length).toBe(0);
+    });
+    test("shows and is accessible", async () => {
+      const { container } = render(
+        <TooltipProvider>
+          <MediaView {...baseProps} waitingForMedia={true} />
+        </TooltipProvider>,
+      );
+      expect(await axe(container)).toHaveNoViolations();
+      expect(screen.getByText("Waiting for media...")).toBeVisible();
+    });
+  });
+
   describe("unencryptedWarning", () => {
     test("is shown and accessible", async () => {
       const { container } = render(