In this commit, we fix a flake in the
`TestRbfChannelFlushingTransitions/early_offer` test. The fix is simple:
this is actually an "iteration", as we have a self transition to the
ChannelNegotiation state first. We also don't need to send the
remoteOffer, so we set `sendInit` to false. The offer still needs to be
passed in to ensure that the assertions work however.
In this commit, we update the RBF state machine to handle early offer
cases. This can happen if after we send out shutdown (to kick things
off), the remote party sends their offer early. This can also happen if
their outgoing shutdown (to ACK ours) was delayed for w/e reason, and we
get their offer first.
The alternative was to modify the state machine itself, but we feel that
handling this early case is better in line with the Robustness principle.
In this commit, we implement the latest version of the RBF loop as
described in the spec. We remove the self loop back based on sending or
receiving shutdown. Instead, from the ClosePending state, we can trigger
a new loop by sending SendOfferEvent (we bump), or OfferReceivedEvent
(they bump).
We also update the rbf state machine w/ the new close addr logic. This
log ensures that the remote party always sends our current address, and
that if they send a new address, we'll update our view of it, and
counter sign the correct transaction.
We also add a CloseErr state. With this new state, we can ensure that
we're able to properly report errors back to the RPC client, and also
optionally force a reconnection or send a warning to the remote party.
