Correct handling of reorg'd-out revoked counterparty transactions

Correct handling of reorg'd-out revoked counterparty transactions

Previously, while processing a confirmed revoked counterparty
commitment transaction, we'd populate `OnchainEvent`s for live
HTLCs with a `txid` source of the txid of the latest counterparty
commitment transactions, not the confirmed revoked one. This meant
that, if the user is using `transaction_unconfirmed` to notify us
of reorg information, we'd end up not removing the entry if the
revoked commitment transaction was reorg'd out. This would
ultimately cause us to spuriously resolve the HTLC(s) as the chain
advanced, even though we were doing so based on a now-reorged-out
transaction.

Luckily the fix is simple - set the correct txid in the
`OnchainEventEntry`. We also take this opportunity to update
logging in a few places with the txid of the transaction causing an
event.