[core] Add SEND_RTCP_MESSAGE

We utilize: https://github.com/sipcapture/hepipe.js to monitor RTCP for our calls. As such, it's super helpful to get the sent RTCP data along with the received RTCP data. The new: SEND_RTCP_MESSAGE basically mirrors the existing RECV_RTCP_MESSAGE.

src/switch_event.c

@@ -207,6 +207,7 @@ static char *EVENT_NAMES[] = {
 	"SEND_INFO",
 	"RECV_INFO",
 	"RECV_RTCP_MESSAGE",
+	"SEND_RTCP_MESSAGE",
 	"CALL_SECURE",
 	"NAT",
 	"RECORD_START",