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/TrigL2LongLivedParticles/python/TrigL2LongLivedParticlesConfig.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 TrigL2LongLivedParticles.TrigL2LongLivedParticlesConf import MuonCluster
 from TrigL2LongLivedParticles.TrigL2LongLivedParticlesConf import MuonClusterIsolation
@@ -6,9 +6,6 @@ from TrigL2LongLivedParticles.TrigL2LongLivedParticlesConf import TrigMuonJetFex
 from TrigL2LongLivedParticles.TrigL2LongLivedParticlesConf import TrigJetSplitter
 from TrigL2LongLivedParticles.TrigL2LongLivedParticlesConf import TrigBHremoval
 
-from AthenaCommon.GlobalFlags import globalflags
-from AthenaCommon.AppMgr import ServiceMgr
-
 
 def getJetSplitterInstance( instance, logratio, pufixlogratio ):