Store buffer after creating it. (#4186)

* Refactor receiver and buffer into Base and higher layer.

To be able to share code/functionality with relay.

* WIP

* WIP

* WIP

* WIP

* WIP

* WIP

* WIP

* WIP

* clean up

* deps

* fix test

* fix test

* Store buffer after creating it.

Also changing signature of creator function as it could call TrackInfo()
and get into a deadlock.

* fix double unlock

* add some more debug logging

pkg/sfu/buffer/buffer_base.go

@@ -1411,7 +1411,7 @@ func (b *BufferBase) seedKeyFrame(keyFrameSeederGeneration int32) {
 	//
 	// send gratuitous PLIs for some time or until a key frame is seen to
 	// get the engine rolling
-	b.logger.Debugw("starting key frame seeder")
+	b.logger.Debugw("starting key frame seeder", "generattion", keyFrameSeederGeneration)
 	timer := time.NewTimer(30 * time.Second)
 	defer timer.Stop()
 
@@ -1423,20 +1423,24 @@ func (b *BufferBase) seedKeyFrame(keyFrameSeederGeneration int32) {
 	rtpStats := b.rtpStats
 	b.RUnlock()
 	if rtpStats == nil {
-		b.logger.Debugw("cannot do key frame seeding without stats")
+		b.logger.Debugw("cannot do key frame seeding without stats", "generation", keyFrameSeederGeneration)
 		return
 	}
 	initialCount, _ = rtpStats.KeyFrame()
 
 	for {
 		if b.isClosed.Load() || b.keyFrameSeederGeneration.Load() != keyFrameSeederGeneration {
-			b.logger.Debugw("stopping key frame seeder: stopped")
+			b.logger.Debugw(
+				"stopping key frame seeder: stopped",
+				"generation", keyFrameSeederGeneration,
+				"currentGeneration", b.keyFrameSeederGeneration.Load(),
+			)
 			return
 		}
 
 		select {
 		case <-timer.C:
-			b.logger.Debugw("stopping key frame seeder: timeout")
+			b.logger.Debugw("stopping key frame seeder: timeout", "generation", keyFrameSeederGeneration)
 			return
 
 		case <-ticker.C:
@@ -1444,6 +1448,7 @@ func (b *BufferBase) seedKeyFrame(keyFrameSeederGeneration int32) {
 			if cnt > initialCount {
 				b.logger.Debugw(
 					"stopping key frame seeder: received key frame",
+					"generation", keyFrameSeederGeneration,
 					"keyFrameCountInitial", initialCount,
 					"keyFrameCount", cnt,
 					"lastKeyFrame", last,