CLEANUP: conn_stream: rename the stream endpoint flags CS_EP_* to  SE_FL_*

Let's now use the new flag names for the stream endpoint.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index bcb2a81..878b44c 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -213,7 +213,7 @@
 
 	qc_stream_desc_release(qcs->stream);
 
-	BUG_ON(qcs->endp && !se_fl_test(qcs->endp, CS_EP_ORPHAN));
+	BUG_ON(qcs->endp && !se_fl_test(qcs->endp, SE_FL_ORPHAN));
 	cs_endpoint_free(qcs->endp);
 
 	eb64_delete(&qcs->by_id);
@@ -1499,15 +1499,15 @@
 
  end:
 	if (b_data(&qcs->rx.app_buf)) {
-		se_fl_set(qcs->endp, CS_EP_RCV_MORE | CS_EP_WANT_ROOM);
+		se_fl_set(qcs->endp, SE_FL_RCV_MORE | SE_FL_WANT_ROOM);
 	}
 	else {
-		se_fl_clr(qcs->endp, CS_EP_RCV_MORE | CS_EP_WANT_ROOM);
-		if (se_fl_test(qcs->endp, CS_EP_ERR_PENDING))
-			se_fl_set(qcs->endp, CS_EP_ERROR);
+		se_fl_clr(qcs->endp, SE_FL_RCV_MORE | SE_FL_WANT_ROOM);
+		if (se_fl_test(qcs->endp, SE_FL_ERR_PENDING))
+			se_fl_set(qcs->endp, SE_FL_ERROR);
 
 		if (fin)
-			se_fl_set(qcs->endp, CS_EP_EOI);
+			se_fl_set(qcs->endp, SE_FL_EOI);
 
 		if (b_size(&qcs->rx.app_buf)) {
 			b_free(&qcs->rx.app_buf);
@@ -1570,7 +1570,7 @@
 }
 
 /* Loop through all qcs from <qcc>. If CO_FL_ERROR is set on the connection,
- * report CS_EP_ERR_PENDING|CS_EP_ERROR on the attached conn-streams and wake
+ * report SE_FL_ERR_PENDING|SE_FL_ERROR on the attached conn-streams and wake
  * them.
  */
 static int qc_wake_some_streams(struct qcc *qcc)
@@ -1586,9 +1586,9 @@
 			continue;
 
 		if (qcc->conn->flags & CO_FL_ERROR) {
-			se_fl_set(qcs->endp, CS_EP_ERR_PENDING);
-			if (se_fl_test(qcs->endp, CS_EP_EOS))
-				se_fl_set(qcs->endp, CS_EP_ERROR);
+			se_fl_set(qcs->endp, SE_FL_ERR_PENDING);
+			if (se_fl_test(qcs->endp, SE_FL_EOS))
+				se_fl_set(qcs->endp, SE_FL_ERROR);
 
 			if (qcs->subs) {
 				qcs_notify_recv(qcs);