This commit updates the messages sent during a single funder workflow
to utilize revocation keys rather than revocation hashes. This now
matches the latest updates to the commitment transaction.
The changes to the workflow are as follows:
* the response message now carries the responder’s revocation key
* the complete message now carries the initiator’s revocation key
Once the initiator receives the response message, it can construct both
versions of the commitment transaction as it now knows the responder’s
commitment key. The initiator then sends their initial revocation key
over to the responder allowing it to construct the commitment
transactions and give the initiator a sig for their version.
This commit modifies most of the wire messages to uniquely identify any
*active* channels by their funding output. This allows the wire
protocol to support funding transactions which open several channels in
parallel.
Any pending channels created by partial completion of the funding
workflow are to be identified by a uint64 initialized by both sides as
follows: the initiator of the connection starts from 0, while the
listening node starts from (1 << 63). These pending channel identifiers
are expected to be monotonically increasing with each new funding
workflow between two nodes. This identifier is volatile w.r.t to each
connection initiation.
