[WIP] Refactor chef finder methods into a single module

Refactor the chef finders into a single module, then include them into *Objects.

This can help in debugging and profiling the chef queries, and keeps the syntax consistent across the *Object classes.

The existing methods were covered by tests (#1041), to ensure the API won't change. Also, they now emit a deprecation warning to help in transitioning to the new syntax.

The patch set is currently not field tested, which is why its marked WIP.
So it turns out the benchmark will only run when log_level is DEBUG which is great. Maybe worth mentioning here, too so people who don't know the insides of ActiveRecord's benchmark don't have to check it?