In this commit, we create a new chainfee package, that houses all fee
related functionality used within the codebase. The creation of this new
package furthers our long-term goal of extracting functionality from the
bloated `lnwallet` package into new distinct packages. Additionally,
this new packages resolves a class of import cycle that could arise if a
new package that was imported by something in `lnwallet` wanted to use
the existing fee related functions in the prior `lnwallet` package.
In this commit, we update the `CommitSpendNoDelay` method to be aware of
the alternate spending mechanism for commitments that don't have a tweak
for the remote party's non-delay output. We also add a new witness type
so callers can convey their expected signing path.
This commit is a step to split the lnwallet package. It puts the Input
interface and implementations in a separate package along with all their
dependencies from lnwallet.
In this commit, we update the `getInputWitnessSizeUpperBound` and all
its callers to be aware of nested p2sh witness inputs. We do so by
adding another bool which is true if the output is a nested p2sh output.
If so, then in order to properly estimate the total weight, the caller
needs to factor in the non-witness data of the additional sigScript data
push.
In this commit, we extend the WitnessGenerator type to now return an
InputScript. This allows it to be more encompassing, as now callers can
expect a sigScript to be populated if the input being swept requires a
sigScript field.
Along the way, we've also renamed input.BuildWitness to
input.CraftInputScript. We also take a step towards allowing the
sweeper to sweep transactions for n2pwkh outputs. We do so by modifying
the BuiltWitness method to instead return an InputScript. Additionally,
when populating inputs if a sigScript is present, it will now be
populated.
