Trk::Track Add move ctor and assignment, do not implement copy via assignment

Two changes

1. Add move copy and assignment operators
2. The copy ctor was implemented via the assignment. In reality copy ctor constructs a new object, so "reseting" its payload is not needed. In general assignment needs one extra step 1st. Avoid this and factor the common code the seem that led to that to a seperate method.

This merge request affects 1 package:

• Tracking/TrkEvent/TrkTrack

Adding @amorley as watcher

added Tracking master review-pending-level-1 labels

CI Result SUCCESS (hash e1073fcd)

	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 19201]

tests pass, changes seem straightforward. L1 approving.

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

merged

mentioned in commit 64f98942

added sweep:ignore label