LArG4FCAL+LArG4FastSimSvc: cmake cleanup, enable flake8

Remove unused external dependencies, update link dependencies and enable flake8.

This merge request affects 2 packages:

• LArCalorimeter/LArG4/LArG4FCAL
• LArCalorimeter/LArG4/LArG4FastSimSvc

Affected files list will not be printed in this case

Adding @pavol as watcher

added JetEtmiss LAr Simulation master review-pending-level-1 labels

CI Result SUCCESS (hash 127d35df)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 24025]

code changes seem fine, CI passed, approving.

Roman(L1)

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 73be345d

added sweep:ignore label