Rename discarded_primary_packets to packets_discarded.

This it what it is called in the spec:
https://w3c.github.io/webrtc-stats/#dom-rtcreceivedrtpstreamstats-packetsdiscarded

Also log the metric in neteq_rtpplay.

Bug: webrtc:8199
Change-Id: Ie0262d17b913eb6949daa703844d90327eee0aa4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/263725
Reviewed-by: Minyue Li <minyue@webrtc.org>
Commit-Queue: Jakob Ivarsson‎ <jakobi@webrtc.org>
Reviewed-by: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37063}
diff --git a/modules/audio_coding/acm2/acm_receiver.cc b/modules/audio_coding/acm2/acm_receiver.cc
index aa98169..f70b37c 100644
--- a/modules/audio_coding/acm2/acm_receiver.cc
+++ b/modules/audio_coding/acm2/acm_receiver.cc
@@ -302,13 +302,12 @@
       neteq_lifetime_stat.removed_samples_for_acceleration;
   acm_stat->fecPacketsReceived = neteq_lifetime_stat.fec_packets_received;
   acm_stat->fecPacketsDiscarded = neteq_lifetime_stat.fec_packets_discarded;
+  acm_stat->packetsDiscarded = neteq_lifetime_stat.packets_discarded;
 
   NetEqOperationsAndState neteq_operations_and_state =
       neteq_->GetOperationsAndState();
   acm_stat->packetBufferFlushes =
       neteq_operations_and_state.packet_buffer_flushes;
-  acm_stat->packetsDiscarded =
-      neteq_operations_and_state.discarded_primary_packets;
 }
 
 int AcmReceiver::EnableNack(size_t max_nack_list_size) {