Since we will use peer flap rate to determine how we rate limit, we
store this value on disk per peer per channel. This allows us to
restart with memory of our peers past behaviour, so we don't give badly
behaving peers have a fresh start on restart. Last flap timestamp is
stored with our flap count so that we can degrade this all time flap
count over time for peers that have not recently flapped.
As we add more elements to the chanfitness subsystem, we will require
more complex testing. The current tests are built around the inability
to mock subscriptions, which is remedied by addition of our own mock.
This context allows us to run the full store in a test, rather than
having to manually spin up the main goroutine. Mocking our subscriptions
is required so that we can block our subscribe updates on consumption,
using the real package provides us with no guarantee that the client
receives the update before shutdown, which produces test flakes.
This change also makes a move towards separating out the testing of our
event store from testing the underlying event logs to prepare for
further refactoring.
