bkpr: for zerconfs, we still wanna know you're opening a channel

We need a record of the channel account before you start sending
payments through it. Normally we don't start allowing payments to be
sent until after the channel has locked in but zeroconf does away with
this assumption.

Instead we push out a "channel_proposed" event, which should only show
up for zeroconfs.

lightningd/dual_open_control.c

@@ -1750,7 +1750,8 @@ static void handle_channel_locked(struct subd *dualopend,
 			  REASON_UNKNOWN,
 			  "Lockin complete");
 	channel_record_open(channel,
-			    short_channel_id_blocknum(channel->scid));
+			    short_channel_id_blocknum(channel->scid),
+			    true);
 
 	/* Empty out the inflights */
 	wallet_channel_clear_inflights(dualopend->ld->wallet, channel);