Add task queue to RtpRtcpInterface::Configuration.

Let ModuleRtpRtcpImpl2 use the configured value instead of
TaskQueueBase::Current().

Intention is to allow construction of RtpRtcpImpl2 on any thread.
If a task queue is provided (required for periodic rtt updates), the
destruction of the object must be done on that same task queue.

Also, delete ModuleRtpRtcpImpl2::Create, callers updated to use std::make_unique.

Bug: None
Change-Id: I412b7b1e1ce24722ffd23d16aa6c48a7214c9bcd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/199968
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32949}

modules/rtp_rtcp/source/rtp_rtcp_interface.h

@@ -18,6 +18,7 @@
 #include "absl/types/optional.h"
 #include "api/frame_transformer_interface.h"
 #include "api/scoped_refptr.h"
+#include "api/task_queue/task_queue_base.h"
 #include "api/transport/webrtc_key_value_config.h"
 #include "api/video/video_bitrate_allocation.h"
 #include "modules/rtp_rtcp/include/receive_statistics.h"
@@ -86,6 +87,11 @@ class RtpRtcpInterface : public RtcpFeedbackSenderInterface {
     RtcpCnameCallback* rtcp_cname_callback = nullptr;
     ReportBlockDataObserver* report_block_data_observer = nullptr;
 
+    // For RtpRtcpImpl2 only. Used for periodic RTT updates, when rtt_stats
+    // (above) is non-null. If provided, destruction of the RtpRtcp object must
+    // occur on this task queue, while construction is allowed on any thread.
+    TaskQueueBase* task_queue = nullptr;
+
     // Estimates the bandwidth available for a set of streams from the same
     // client.
     RemoteBitrateEstimator* remote_bitrate_estimator = nullptr;