[enhancement] Add PrivExchange

It is only relevant for exchange servers: https://dirkjanm.io/abusing-exchange-one-api-call-away-from-domain-admin/
If you want to keep the core checks clean from application specific checks that may only work on a small subset of hosts, you may consider to add a switch for extended checks that contains stuff like this or so... I expect the future to bring a lot more of these