hls muxer / source: route AAC units singularly

This aligns the HLS implementation with the rest of the server. In case
of HLS/MPEGTS, the server now generates an ADTS packet for each AU,
without grouping multiple AUs into a single ADTS packet.

internal/core/hls_source.go

@@ -119,12 +119,12 @@ func (s *hlsSource) run(ctx context.Context) error {
 		}
 	}
 
-	onAudioData := func(pts time.Duration, aus [][]byte) {
+	onAudioData := func(pts time.Duration, au []byte) {
 		if stream == nil {
 			return
 		}
 
-		pkts, err := audioEnc.Encode(aus, pts)
+		pkts, err := audioEnc.Encode([][]byte{au}, pts)
 		if err != nil {
 			return
 		}