Add additional log checkpoint information

[directionless]

In thinking about how to add more information to the checkpoint logs it felt like this needed to become a struct -- easier to hold some state, add a querier, and whatnot.

1. Refactor to a checkpointer struct, moved the Run around a little
2. Add a SetQuerier function
3. When there is a querier, additional things are queried.

Fixes: #1061

[James-Pickett]

Nice!