WebRTC congestion control (#26)

* Add congestion control

* Improve stream matching, add manual stream selection, add metrics

* Use a ticker for bitrate estimation and make bandwidth drops switch to lower streams more aggressively

* Missing signal response, fix video auto bug

* Remove redundant mutex

* Bitrate history queue

* Get bitrate fn support h264 & float64

---------

Co-authored-by: Aleksandar Sukovic <aleksandar.sukovic@gmail.com>

internal/capture/buckets/buckets_test.go

@@ -0,0 +1,83 @@
+package buckets
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/demodesk/neko/pkg/types"
+	"github.com/demodesk/neko/pkg/types/codec"
+)
+
+func TestBucketsManagerCtx_FindNearestStream(t *testing.T) {
+	type fields struct {
+		codec   codec.RTPCodec
+		streams map[string]types.StreamSinkManager
+	}
+	type args struct {
+		peerBitrate int
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   types.StreamSinkManager
+	}{
+		{
+			name: "findNearestStream",
+			fields: fields{
+				streams: map[string]types.StreamSinkManager{
+					"1": mockStreamSink{
+						id:      "1",
+						bitrate: 500,
+					},
+					"2": mockStreamSink{
+						id:      "2",
+						bitrate: 750,
+					},
+					"3": mockStreamSink{
+						id:      "3",
+						bitrate: 1000,
+					},
+					"4": mockStreamSink{
+						id:      "4",
+						bitrate: 1250,
+					},
+					"5": mockStreamSink{
+						id:      "5",
+						bitrate: 1700,
+					},
+				},
+			},
+			args: args{
+				peerBitrate: 950,
+			},
+			want: mockStreamSink{
+				id:      "2",
+				bitrate: 750,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			m := BucketsNew(tt.fields.codec, tt.fields.streams, []string{})
+
+			if got := m.findNearestStream(tt.args.peerBitrate); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("findNearestStream() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+type mockStreamSink struct {
+	id      string
+	bitrate int
+	types.StreamSinkManager
+}
+
+func (m mockStreamSink) ID() string {
+	return m.id
+}
+
+func (m mockStreamSink) Bitrate() int {
+	return m.bitrate
+}