[audio] Plumbing of ReportBlockData from RTCPReceiver to MediaSenderInfo

This is part of implementing RTCRemoteInboundRtpStreamStats. The CL was
split up into smaller pieces for reviewability. Spec:
https://w3c.github.io/webrtc-stats/#dom-rtcremoteinboundrtpstreamstats

In [1], ReportBlockData was implemented and tested.
This CL adds the plumbing to make it available in MediaSenderInfo for
audio streams, but the code is not wired up to make use of these stats.

In follow-up CL [2], ReportBlockData will be used to implement
RTCRemoteInboundRtpStreamStats. The follow-up CL will add integration
tests exercising the full code path.

[1] https://webrtc-review.googlesource.com/c/src/+/136584
[2] https://webrtc-review.googlesource.com/c/src/+/138067

Bug: webrtc:10455
Change-Id: Id8940090cc9c121e8f06ccdb068a22ce24c07092
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138066
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28072}

modules/rtp_rtcp/source/rtp_rtcp_impl.cc

@@ -589,6 +589,11 @@ int32_t ModuleRtpRtcpImpl::RemoteRTCPStat(
   return rtcp_receiver_.StatisticsReceived(receive_blocks);
 }
 
+std::vector<ReportBlockData> ModuleRtpRtcpImpl::GetLatestReportBlockData()
+    const {
+  return rtcp_receiver_.GetLatestReportBlockData();
+}
+
 // (REMB) Receiver Estimated Max Bitrate.
 void ModuleRtpRtcpImpl::SetRemb(int64_t bitrate_bps,
                                 std::vector<uint32_t> ssrcs) {