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).
We need the newer version of lndclient to get our synced to chain
state. This requires changes to our test mock, so it is separated
into a different commit. Since lndclient is expanding to be used in
projects other than loop, the client interface is embedded in our
mock rather than implementing functions we do not need. Functions that
we already use in tests are updated accordingly.
Note that while this commit bumps us to a version of lndclient that
defaults to requiring lnd 0.11, we do not bump our required version
yet because we are not using any new endpoints.
