Remove all cmt files

Removing all cmt files (requirements and project) as CMT is no longer supported as from Gaudi v28r0 (LHCb v42r1).

Removing completely the LCG_Generators_Interfaces and LCG_Setting packages as the former only contained requirements to resolve the path in LCG_XX/MCGenerators where to find the generator library and linking (now done via cmake/FindGENNAME.cmake) and the latter was needed for the LCG_Generators_Interfaces packages to work.