use new implementation of MET corrections in PAT jetTools and start refactoring the MET uncertainty tool

This PR replaces the old implementation of CaloMET corrections in PAT jetTools with the new one.

We are preparing to delete the old implementation (https://github.com/cms-sw/cmssw/pull/4014).

Incidentally, we plan to discontinue configuring MET corrections in jetTools. The plan was made a while ago (see slide2 https://indico.cern.ch/event/187209/contribution/3) but hasn't been implemented.