Furhter cleanup of Particle Calo Extension Tool

Mentioning @mhodgkin

3 main changes here

• Use nullptr instead of dummy CaloExtension objects. Could help save space/allocations

• Use the same code for electrons as for muons or pions. Still an electron is treated as muon (since this closer to non interacting``

• Remove a a dynamic_cast from EMExtrapolationTools and some superfluous DEBUG loop.

This merge request affects 2 packages:

• Reconstruction/RecoTools/TrackToCalo
• Reconstruction/egamma/egammaTrackTools

added Egamma Reconstruction master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-24422-2019-06-25-05-51
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 626]

This looks ok, approving. Catrin (L1)

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

merged

mentioned in commit fb7bd02c

added sweep:ignore label