ATLASRECTS-5666: Migration of JetFitter package to a modularised version in AthenaMT

Description: A new modularised version of the package tested in 21.2. This is the migration to AthenaMT The code runs in both the split and usual b-tagging configuration as defined in https://gitlab.cern.ch/atlas/athena/-/blob/master/PhysicsAnalysis/JetTagging/JetTagAlgs/BTagging/python/BTagRun3Config.py

There are several differences between the 21.2 and the master versions, due to the different environments. Configuration python files are provided in the BTagging/python folder, while keeping (for the time being?) the old JetFitter configuration files.

Tagging @cpollard, @sanmay, @cschiavi, @vdao , @dguest and @guirriec.

Jira: ATLASRECTS-5666