Using ParameterSet in SingleFreeTrackParameters

[FabianKlimpel]

This PR replaces the plain storage of data by the ParameterSet as performed in SingleTrackParameters.
It is a component of #165.

[codecov]

Codecov Report

Merging #268 into master will increase coverage by 3.56%.
The diff coverage is 44.71%.

@@            Coverage Diff             @@
##           master     #268      +/-   ##
==========================================
+ Coverage   44.84%   48.41%   +3.56%     
==========================================
  Files         376      319      -57     
  Lines       18866    16336    -2530     
  Branches     8970     7570    -1400     
==========================================
- Hits         8461     7909     -552     
+ Misses       4905     3175    -1730     
+ Partials     5500     5252     -248     

Impacted Files	Coverage Δ
...Acts/EventData/detail/initialize_parameter_set.hpp	81.81% <ø> (ø)
...include/Acts/TrackFinder/CKFSourceLinkSelector.hpp	47.82% <ø> (ø)
Core/include/Acts/Utilities/Helpers.hpp	58.90% <ø> (ø)
...clude/Acts/Vertexing/AdaptiveMultiVertexFinder.ipp	44.59% <0.00%> (ø)
Core/src/Geometry/CutoutCylinderVolumeBounds.cpp	40.29% <0.00%> (ø)
...lude/Acts/Visualization/EventDataVisualization.hpp	41.00% <30.00%> (-1.47%)	⬇️
Core/src/Visualization/GeometryVisualization.cpp	34.51% <34.51%> (ø)
Core/src/Geometry/ProtoLayerHelper.cpp	48.71% <36.36%> (-14.44%)	⬇️
Core/include/Acts/EventData/ParameterSet.hpp	91.17% <88.88%> (ø)
Core/include/Acts/EventData/Measurement.hpp	63.82% <100.00%> (-2.18%)	⬇️
... and 61 more

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[msmk0]

Straightforward changes. Looks good to me. The two comments only request minor changes to confirm to our naming guidelines.