While trying to solve a reconciliation mystery, alexander.gorrod@mongodb.com added some stats counting reconciliation calls for pages over 100MB, 10MB-100BM, and 1MB-10MB. This is generally useful, so here's a ticket to add those stats in.

Another potential addition here would be some sort of diagnostic check for super-large pages, e.g. over 100MB. This is less obvious because sometimes it's legitimate – e.g. if you have 99MB keys, all bets are off. Either way it probably ought to be an option.