METReconstruction: calculate dR directly

The MET reconstruction need to retrieve the clusters around 0.2 cone of the tau candidate. Since the vertex of the tau candidate could be different from PV0, a vertex correction is needed. The corrected clusters are decorated onto the tau candidate, but is transient only. This break the MET reconstruction from ESD/AOD. After recent development of tau reconstruction, the correction is now much simple, and we could do it directly in METReconstruction.

This should fix ATLASRECTS-5793.