This commit modifies the sweeper store to save a `TxRecord` in db
instead of an empty byte slice. This record will later be used to bring
RBF-awareness to our sweeper.
We remove the publishing of the last published sweep tx during the
startup of the sweeper. This republishing can lead to situations
where funds of the default wallet might be locked for neutrino
backend clients.
Moreover all related tests are removed as well.
