L1Calo eFEX algorithm migration

Pretty much complete version of the eFEX EM and Tau algorithms

• Separate clustering work into tools
• removed common base class of EM and Tau alg (there was little in common)
• ready to become re-entrant in master:
  • removed class members (except properties, tools)
  • const-ness wherever possible
• fabs -> std::abs (clang)
• removed histogramming as discussed (different in rel 22)
• move to datahandles (use writehandle for eFEX EM, not sure this works in 21.3 - to be tested)
• move to LVL1 namespace as all classes in this package
• small python code snipped that can be used to include both algs in the l1sim sequence

The same code is also maintained in 21.3 for the coming months, so some code is not yet at the rel22 standard.

Also the latest developments from the 21.3 release (from Alan Watson) are contained in this request.

@bcarlson @jburr @afaulkne @watsona