Add toString to TrackGroup(Array)

These classes are often logged in error messages or tests. The
current output is just the hash code which makes it hard to debug.

PiperOrigin-RevId: 736799086
(cherry picked from commit 54c64b4)

Author: tonihei

libraries/common/src/main/java/androidx/media3/common/TrackGroup.java

@@ -161,6 +161,11 @@ public boolean equals(@Nullable Object obj) {
     return id.equals(other.id) && Arrays.equals(formats, other.formats);
   }
 
+  @Override
+  public String toString() {
+    return id + ": " + Arrays.toString(formats);
+  }
+
   private static final String FIELD_FORMATS = Util.intToStringMaxRadix(0);
   private static final String FIELD_ID = Util.intToStringMaxRadix(1);
 

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/TrackGroupArray.java

@@ -115,6 +115,11 @@ public boolean equals(@Nullable Object obj) {
     return length == other.length && trackGroups.equals(other.trackGroups);
   }
 
+  @Override
+  public String toString() {
+    return trackGroups.toString();
+  }
+
   private static final String FIELD_TRACK_GROUPS = Util.intToStringMaxRadix(0);
 
   public Bundle toBundle() {