Eliminate back links in Run2 to Run 3 navigation converter
This MR contains a fix eliminating the possibility to produce backlinks during the conversion.
A set of new nodes created in a given chain processing is added. The nodes that are in this set are not allowed to be reused. The reuse of nodes created in processing other chains is not constrained and thus the compression works as before.
In addition, small refactors that limited the scope of variables (avoid clearing/resetting and reduces a chance of unintended use out of real scope of validity). Renamed sorting functor ordered_sorter to: rois_priority_order as it better describes what it does.
Plus some other minor changes.
Conversion of the chain HLT_mu4_j80_xe80_pufit_2dphi10_L1MU4_J50_XE50_DPHI-J20s2XE30 where the issue occured is still somewhat faulty because there is an additional link to object that is not in store. Once this is resolved we should make convertion fo this chain a unit test.