Restrict `ChannelManager` persist in fuzzing to when we're told to

Restrict `ChannelManager` persist in fuzzing to when we're told to

In the `chanmon_consistency` fuzz, we currently "persist" the
`ChannelManager` on each loop iteration. With the new logic in the
past few commits to reduce the frequency of `ChannelManager`
persistences, this behavior now leaves a gap in our test coverage -
missing persistence notifications.

In order to cath (common-case) persistence misses, we update the
`chanmon_consistency` fuzzer to no longer persist the
`ChannelManager` unless the waker was woken and signaled to
persist, possibly reloading with a previous `ChannelManager` if we
were not signaled.