Rewrite Channel resend tracking to make it much more reliable

Rewrite Channel resend tracking to make it much more reliable

Resending revoke_and_ack and commitment_signed (+update) messages
after monitor-update-failure or disconnection has been a highly
unreliable part of our codebase for some time (as evidenced by the
number of bugs caught in the chanmon_fail_consistency fuzz target).
This is due to its rather ad-hoc nature and tracking/behavior which
consists of checking a number of different flags to try to deduce
which messages were/were not delivered and go from there. Instead,
this commit rewrites it to simply keep track of the order messages
were generated originally, as we always resend in the
originally-generated order.

I'm anticipating this will be way more robust than the old code, in
addition to its simplicity.