staticbackup: don't use wireaddr_internal.

This is an internal type: it has no API guarantees (indeed, I'm about
to change it, which is how I discovered scb was using it).

Fortunately for every case we care about, it is actually a wireaddr
(in theory the peer can connect locally using a local socket, but this
is mostly for testing and is a very strange setup, and so simply don't
do scb for those).

In this case, the wire encoding is a single byte followed by the
wireaddr, so open-code that in scb_wire.csv for compatibility.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/scb_wire.csv

@@ -10,10 +10,12 @@ subtype,scb_chan
 subtypedata,scb_chan,id,u64,
 subtypedata,scb_chan,cid,channel_id,
 subtypedata,scb_chan,node_id,node_id,
-subtypedata,scb_chan,addr,wireaddr_internal,
+subtypedata,scb_chan,unused,u8,
+subtypedata,scb_chan,addr,wireaddr,
 subtypedata,scb_chan,funding,bitcoin_outpoint,
 subtypedata,scb_chan,funding_sats,amount_sat,
 subtypedata,scb_chan,type,channel_type,
+
 msgtype,static_chan_backup,6135,
 msgdata,static_chan_backup,version,u64,
 msgdata,static_chan_backup,timestamp,u32,