[QoL] Add ROOT CLI compatibility for GeomUtils + macro for single det overlaps check

Quite straightforward, just copying the logic used for the McbmUtils
Found because needed to make a macro for "single geo overlap checks", but should be useful in general to just have all these available (almost) transparently in ROOT (as for the McbmUtils, one need two extra lines creating an empty instance of the dummy class ToForceLibLoad to get it loaded)

The macro is mostly similar to the one for the full setups (check_overlaps.C) on which it is based, but inherits more TopNode loading/detection options from scan_geom.C
=> I suspect that it would be incompatible with full setup geo files and therefore I did not attempt to merge them, as it was not worth the effort (two working macros with proper names for separate case)

Ready but not pressing/urgent, created the MR mainly to cleanup my local git folder and make it easier to reference if somebody need the "single geo overlap checks" macro during MR reviews