Fuzz reloading with a stale monitor in chanmon_consistency

Fuzz reloading with a stale monitor in chanmon_consistency

Now that we are gearing up to support fully async monitor storage,
we really need to fuzz monitor updates not completing before a
reload, which we do here in the `chanmon_consistency` fuzzer.

While there are more parts to async monitor updating that we need
to fuzz, this at least gets us started by having basic async
restart cases handled. In the future, we should extend this to make
sure some basic properties (eg claim/balance consistency) remain
true through `chanmon_consistency` runs.