Prevent infinite reloads when CAN-BLOCK-RELOAD=YES is not honored

Waits for half the part target duration before retrying when the server responds with
`CAN-BLOCK-RELOAD=YES` but does not actually block until the playlist updates.
Prevents excessive requests in such cases.

Author: mojsdev

RELEASENOTES.md

@@ -80,6 +80,8 @@
 *   Cronet extension:
 *   RTMP extension:
 *   HLS extension:
+    *   Prevent excessive reloads by waiting for half the part target duration
+        when `CAN-BLOCK-RELOAD=YES` is not honored.
 *   DASH extension:
 *   Smooth Streaming extension:
 *   RTSP extension:

libraries/exoplayer_hls/src/main/java/androidx/media3/exoplayer/hls/playlist/DefaultHlsPlaylistTracker.java

@@ -853,6 +853,13 @@ private void processLoadedPlaylist(
             playlistSnapshot != oldPlaylist
                 ? playlistSnapshot.targetDurationUs
                 : (playlistSnapshot.targetDurationUs / 2);
+      } else if (
+          playlistSnapshot == oldPlaylist && playlistSnapshot.partTargetDurationUs != C.TIME_UNSET
+      ) {
+        // To prevent infinite requests when the server responds with CAN-BLOCK-RELOAD=YES but does
+        // not actually block until the playlist updates, wait for half the part target duration
+        // before retrying.
+        durationUntilNextLoadUs = playlistSnapshot.partTargetDurationUs / 2;
       }
       earliestNextLoadTimeMs =
           currentTimeMs + Util.usToMs(durationUntilNextLoadUs) - loadEventInfo.loadDurationMs;