Trigger/TrigAlgorithms: Package cleanup

Cleanup of several packages under Trigger/TrigAlgorithms:

• cleanup cmake configuration
• enable flake8
• delete obsolete job options
• remove CLHEP dependency where applicable

Trigger/TrigAlgorithms/TrigT2HistoPrmVtx/python/TrigT2HistoPrmVtxComboConfig.py

-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 
 from TrigT2HistoPrmVtx.TrigT2HistoPrmVtxConf import TrigT2HistoPrmVtxCombo
 
-
-from AthenaCommon.SystemOfUnits import mm, GeV
-
-
 class TrigT2HistoPrmVtxComboBase (TrigT2HistoPrmVtxCombo):
     __slots__ = []
     def __init__(self, name):