Trk::Track add setFitQuality and isValid method
This follows !37307 (merged) and discussion with @sroe
In short the above basically allows for an almost meaningfull default ctor. A default ctor object though has no fitQuality (nor trackStateOnSurface). Allow to set it (there was already a setter for trackStateOnSurface).
A track without these 2 is invalid
Expand the check added in the previous MR to other methods that will possibly iterate over trackStateOnSurfaces.