Adapted to drop of UT common base classes

Part of the set of MRs LHCb!3369 (merged), !594 (merged), Rec!2670 (merged), Boole!375 (merged)

Also dropped a LOT of unused code. The drops are carefully split into one class/one feature per commit so that the ones that should not be dropped can be easily reverted.

The reason for dropping was always identical : not used and would need non trivial fix to compile.