route: Do not require both directions to be active

This likely lead to a number of false errors when attempting to
route. We deemed a channel to be unusable as soon as either direction
isn't usable. This is bad since it excludes not only zeroconf
channels (which have different scids for the two directions), but it
also excludes any channel that we haven't seen an update from
yet. This was likely introduced when attemting to exclude nodes that
haven't sent a disable, but their peer has, but this is not necessary
as the unresponsive node would be marked as isolated by all its peers,
so we don't need to artificially mark a channel direction as disabled
when really we can't even enter the node to traverse the channel in
that direction.

Changelog-Fixed: routing: Fixed an issue where we would exclude the entire channel if either direction was disabled, or we hadn't seen an update yet.

common/route.c

@@ -25,7 +25,7 @@ bool route_can_carry(const struct gossmap *map,
 		       struct amount_msat amount,
 		       void *arg)
 {
-	if (!c->half[dir].enabled || !c->half[!dir].enabled)
+	if (!c->half[dir].enabled)
 		return false;
 	return route_can_carry_even_disabled(map, c, dir, amount, arg);
 }