MINOR: mux-quic: add traces for 0-copy/fast-forward

Complete qmux traces :
* add a trace when 0-copy is used for DATA transfer
* mark the FIN as detected when using fast forward

src/h3.c

@@ -1776,6 +1776,9 @@ static int h3_resp_data_send(struct qcs *qcs, struct buffer *buf, size_t count)
 		     htx_nbblks(htx) == 1 && type == HTX_BLK_DATA)) {
 		void *old_area = res->area;
 
+		TRACE_DATA("perform zero-copy DATA transfer", H3_EV_TX_DATA,
+		           qcs->qcc->conn, qcs);
+
 		/* map an H2 frame to the HTX block so that we can put the
 		 * frame header there.
 		 */

src/mux_quic.c

@@ -2870,8 +2870,10 @@ static size_t qmux_strm_done_ff(struct stconn *sc)
 
 	TRACE_ENTER(QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
 
-	if (sd->iobuf.flags & IOBUF_FL_EOI)
+	if (sd->iobuf.flags & IOBUF_FL_EOI) {
+		TRACE_STATE("reached stream fin", QMUX_EV_STRM_SEND, qcs->qcc->conn, qcs);
 		qcs->flags |= QC_SF_FIN_STREAM;
+	}
 
 	if (!(qcs->flags & QC_SF_FIN_STREAM) && !sd->iobuf.data)
 		goto end;