Add NetEq config flag that enables RTX handling.

When enabled, the delay manager is updated with reordered packets. It also makes the peak detector ignore the reordered packets.

Change-Id: I2bdc99764cc76b15e613ed3dc75f83aaf66eee4e
Bug: webrtc:10178
Reviewed-on: https://webrtc-review.googlesource.com/c/116481
Commit-Queue: Jakob Ivarsson‎ <jakobi@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26187}

modules/audio_coding/neteq/include/neteq.h

@@ -117,6 +117,7 @@ class NetEq {
     int min_delay_ms = 0;
     bool enable_fast_accelerate = false;
     bool enable_muted_state = false;
+    bool enable_rtx_handling = false;
     absl::optional<AudioCodecPairId> codec_pair_id;
     bool for_test_no_time_stretching = false;  // Use only for testing.
   };