BugFix: fixing MC event indexing scheme of links to MVD MC points
This merge request fixes the bug in the MC-links definition in the MVD digitizer.
Previously, an entry index of MVD link was defined as a global MC event index. It did not affect the simulations with only one transport input, but introduced bugs in the latter stages of reconstruction and analysis, when several inputs (collision, signal and beam) were used and the MC information was required.