child-sa: Add a new state to track rekeyed IKEv1 CHILD_SAs

This is needed to handle DELETEs properly, which was previously done via
CHILD_REKEYING, which we don't use anymore since 5c6a62ceb6 as it prevents
reauthentication.

src/libcharon/sa/child_sa.c

@@ -34,6 +34,7 @@ ENUM(child_sa_state_names, CHILD_CREATED, CHILD_DESTROYING,
 	"INSTALLED",
 	"UPDATING",
 	"REKEYING",
+	"REKEYED",
 	"RETRYING",
 	"DELETING",
 	"DESTROYING",