Changed argument of function NewBatcher from LoopOutFetcher to SweepFetcher
(returning new public type SweepInfo).
This change is backwards-incompatible on the package layer, but nobody seems
to use the package outside of Loop.
To use NewBatcher inside Loop, turn loopdb into SweepFetcher using
function NewSweepFetcherFromSwapStore.
Method Store.GetBatchSweeps provides data from tables outside of sweepbatcher:
swaps, loopout_swaps, htlc_keys. It makes it harder to reuse. Batcher already
has a straightforward way to get swap data: LoopOutFetcher interface (loopdb).
In this commit I switch the source of data from the field returned by Store
(LoopOut) to loading independently by calling LoopOutFetcher.FetchLoopOutSwap.
It used to be set to default (defaultBatchConfTarget = 12) which
could in theory affect fee rate if updateRbfRate() and publish()
were not called before the batch was saved. (Unlikely scenario.)
If the sweep was successfully updated in the batch, no need to
try to add it to all other batches.
Added a test reproducing adding a sweep to both batches without this change.
Previously storing an empty batch would make the batcher fail to start
as spinning up a restored batch assumes that there's a primary sweep
added already. As there's no point in spinning up such batch we can just
skip over it.
Furthermore we'll ensure that we won't try to ever publish an empty
batch to avoid setting the fee rate too early.
Previously we'd report the fees per sweep as the total sweep cost of a
batch. With this change the reported cost will be the proportional fee
which should be equal for all sweeps except if there's any rounding
difference in which case that is paid by the sweep belonging to the
first input of the batch tx.
