Add a dated fee budget to our swap suggestions. This budget only applies
to automatically dispatched swaps (which will be added in later
commits). We choose to apply the fee budget to our suggestions so that
they perfectly replicate what the autolooper would do. The budget has a
start date so that it can be refreshed once it has been used up over a
period (rather than having to endlessly increase it).
As we add more parameters in this PR, we wil want to test values
beyond our default values. This commit updates the suggest swaps test
helper to take a full setup struct, and adds a default set of channels
and rules which will be used in the absense of this setup struct.
To decide whether we event want to attempt a swap, we add a fee limit
that we check against our estimate for the current number of
confirmations we want our sweep to confirm in. If fees are higher than
this limit, we do not suggest swaps.
This commit updates swap suggestions to return loop out requests with
sufficient fields populated so that a loop out can directly be
dispatched from a suggestion. This requires setting of fees an min
sweep conf targets (our htlc conf target and addresss will be set by
the daemon's client rpc server if we do not provide them). We also do
some test refactoring so that we can more easily test the suggest swaps
endpoint.
