This incorporates wallet rescanning into the
payment process to restore tx conf functionality
when the wallet gets into an error state. Associated
tests have been added.

This dedicates a lifecycle process for payment
processing and updates the necessary configs.
Payment processing is now triggered via signals
from the chainstate to the payment manager.
Associated tests have been added.

This updates the dividend payment process to
get the lowest failing tx conf height to use for the
start of a wallet rescan to ensure all failing tx confs
are covered.

This fixes an issue where the tx hashes sent in the
notification request were duplicates of each other
because of taking slice of the iterator variable. The
stopAfter param was also updated to send over the
correct parameter (conf count) instead of a
block height.