Migrate extends2, etc. to extends

The explicit extends2, extends3, etc. classes are no longer required and can be replaced by the variadic extends.

This merge request affects 11 packages:

• Calorimeter/CaloDetDescr
• Control/AthenaExamples/AthExHive
• Control/AthenaServices
• PhysicsAnalysis/D3PDMaker/D3PDMakerCoreComps
• PhysicsAnalysis/D3PDMaker/D3PDMakerRoot
• PhysicsAnalysis/D3PDMaker/D3PDMakerUtils
• Simulation/G4Atlas/G4AtlasTools
• Simulation/G4Sim/G4HiveEx
• Tracking/Acts/ActsTrackReconstruction
• Trigger/TrigT1/L1Topo/L1TopoSimulation
• graphics/JiveXML

Affected files list will not be printed in this case

Adding @oliveirg ,@toyamaza ,@pagessin ,@goetz ,@cmorenom ,@tbold ,@iriu ,@jchapman ,@stelzer ,@rbianchi ,@jojungge ,@ssnyder ,@jmharris ,@maszyman ,@paulama ,@asonay ,@orlando ,@pavol ,@cvarni ,@gemmeren as watchers

added ACTS Analysis Calorimeter Core EventDisplay Simulation Tracking Trigger main review-pending-level-1 labels

removed review-pending-level-1 label

added review-approved label

CI Result SUCCESS (hash 382e164c)

	Athena	AthSimulation	AthGeneration	AthAnalysis
externals
cmake
make
tests

Full details available on this CI monitor view. Check the JIRA CI status board for known problems
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AthAnalysis: number of compilation errors 0, warnings 0
For experts only: Jenkins output (remote access info)

merged

mentioned in commit d56ff48c