If the peer is offline when we see the funding txid, we don't actually
update the channel's info. Here, we move it up to where the scid is set,
so that we always update the channel's funding_txid to the correct
(mined) information.
Trying to put all the disconnect logic into the same path was a dumb
idea. If you asked to reconnect but passed in an 'unsaved' channel, we
would not call the 'reconnect' code.
Instead, we make a differentiation between "unsaved" channels
(ones that we haven't received commitment tx for) and handle the
disconnect for these separate from where we want to do a reconnect.
When the funding tx reaches depth, update the channel's data to the
"correct" funding transaction info from inflights (if necessary).
This will be necessary if:
- the transaction has been successfully RBF'd and
- the lesser fee transaction is the one successfully mined, OR
- the channel is in the process of being RBF'd
Prior to this, all reconnect logic lived in channeld. If you
disconnected before we finished building a funding transaction, that was
no big deal. Now, however, we're waiting for the funding to lock in in
dualopend, instead of handing straight to channeld to wait.
So we need a way to restart dualopend.
This will make it possible to do RBF, since we can re-start the opening
process in dualopend while waiting for lock-in.
Note the new channel states are being used, DUALOPEND_INIT and
DUALOPEND_AWAITING_LOCKIN, to differentiate from openingd/channeld opens
