BoundarySurface: Copying vector of shared_ptr is expensive, use reference instead

Copying and deleting vectors of shared_ptrs are an expensive operation. Use a reference where ever possible.

WARNING: big files (>100K) are found in the changeset

124K in file Tracking/TrkExtrapolation/TrkExTools/src/TimedExtrapolator.cxx

264K in file Tracking/TrkExtrapolation/TrkExTools/src/Extrapolator.cxx

This merge request affects 6 packages:

• Tracking/TrkDetDescr/TrkDetDescrTools
• Tracking/TrkDetDescr/TrkGeometry
• Tracking/TrkDigitization/TrkDigTools
• Tracking/TrkExtrapolation/TrkExEngine
• Tracking/TrkExtrapolation/TrkExTools
• Tracking/TrkExtrapolation/TrkExUtils

Adding @jchapman ,@amorley ,@gavrilen as watchers

added Digitization Tracking master review-pending-level-1 labels

CI Result SUCCESS (hash 51ba8e2e)

	Athena	AthSimulation
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
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 10315]

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

merged

mentioned in commit 3e5901e8

added sweep:ignore label