Changes to make Pixel CPE thread safe

Main purpose of this is to make Pixel CPE thread safe.
The following changes were implemented:
- Remove all mutables from Pixel CPE
- Move Si*TempateStore vectors our of Si*Tempate, in order to store Si*TempateStore vectors as non-mutables in *CPE, while keeping the changes to Si*Template minimal
- Remove ClusterParameterEstimator template and force to return pixel QualityWord directy
- Introduce RecoLocalTracker SiPixelRecHits SiPixelGenError, for faster LAwidth computation in CPEGeneric.