raop: implement retransmission

Keep the last relation between the sequence number and the timestamp
(ringbuffer position).

When a retransmission is requested for a given sequence number use the
relation to calculate the corresponding timestamp and retransmit the
packet from the ringbuffer again.

See #5276

src/modules/module-raop-sink.c

@@ -689,6 +689,7 @@ on_control_source_io(void *data, int fd, uint32_t mask)
 		case 0xd5:
 			pw_log_debug("retransmit request seq:%u num:%u", seq, num);
 			/* retransmit request */
+			rtp_stream_resend_packets(impl->stream, seq, num);
 			break;
 		}
 	}