Bug fix in skimmed data (dca for combined tracks) + extension adding number of shared clusters monitoring

[miranov25]

Relates to - #12928

1.) DCA for combined tracks is stored relative to (0,0). It can be recalculated using the vertex position, but some precision is lost in this process.

2.) The number of shared clusters is heavily dependent on the error parameterization and there are indications of possible bug in sector/stack merging, as evidenced by a distribution with a stack-like structure.

In figure below the distribution of the shared clusters for old(blue) and new (red) error parameterization. In new error parameterization it is assumed that amount of the shared clusters will be reduced.