In this commit, we replace the existing min/max duration system with a
single field that expresses the expected duration of a lease. Note that
we've left some of the exiting logic in place that select a duration
from a bid in an attempt to make this more of a "soft fork" which will
allow any existing orders to be cleared out as normal before we switch
over.
Once we add multiple durations (this commit assumes a single duration),
we'll need to modify the verification logic to be able to handle
multiple clearing prices for a given batch.
As a preparation to abandon canceled channels, we first extract the
utility method to locate a channel output created in a batch from the
batch verifier into the batch itself.
As a preparation to avoid package import cycles when introducing more
generic terms, we move the FeeSchedule interface and its
LinearFeeSchedule implementation to the terms package.
In this commit, we change the key stored within the internal order kit
into a raw pubkey array. Along the way we fix a bug in the verifier
tests due to using a map with pointer keys rather than the actual value
itself.
