Some simple initial tests for MediaView (#2813)

* Some simple tests for MediaView

* Use jest-dom assertions

* Add tests for videoMuted

* Add test case for placeholder video track

* Revert yarn.lock changes

* More revert

* Deduplicate test case logic and improve names

* Use role and label

src/tile/MediaView.module.css

@@ -34,10 +34,6 @@ Please see LICENSE in the repository root for full details.
   object-fit: contain;
 }
 
-.media.videoMuted video {
-  display: none;
-}
-
 .bg {
   background-color: var(--cpd-color-bg-subtle-secondary);
   inline-size: 100%;
@@ -47,7 +43,6 @@ Please see LICENSE in the repository root for full details.
 }
 
 .avatar {
-  display: none;
   position: absolute;
   top: 50%;
   left: 50%;
@@ -55,10 +50,6 @@ Please see LICENSE in the repository root for full details.
   pointer-events: none;
 }
 
-.media.videoMuted .avatar {
-  display: initial;
-}
-
 /* CSS makes us put a condition here, even though all we want to do is
 unconditionally select the container so we can use cqmin units */
 @container mediaView (width > 0) {