Added "minimal" config files and merged changes for working retag

Should be a working version including all the the changes from previous retagging tdd repository (in the end not much as you've implemented loads already).

Works locally and should work on grid, no idea why pipeline fails (it also failed immediately when I made a clean copy from atlas-flavor-tagging-tools/training-dataset-dumper:main into a new side branch).

Config file doesn't contain the ftagTruthSourceLabel track variable which apparently caused the issue before as per @dguest's comment.