enable/update jet core iteration for phase-2

[slava77]

as a follow up to CMSTrackerDPG/Tasks#8 (comment)
it's clear now that a regional jetCore tracking will be needed for phase-2.

• The starting point could be to add the legacy-like jetCore using a cluster splitter Track refits based on W-mass analysis #3
• next, an ML-based improvement can be added similar to DeepCore

@emiglior @bouchamaouihichem
please tag more people who may be interested to contribute
https://mattermost.web.cern.ch/cms-exp/channels/trk-pog-deepcore-integration could be used as well for discussion