Revert "Temporarily resurrected old ordering of hits in PrPixelHitManager"

This reverts commit 7931c3e1

That commit was part of !858 (merged) as a temporary measure to not have changing output due to a fix on sorting (see comments in the code for details). It was basically reverting the fix. It is now time to to revert the commit and thus put back the fix. Expect slight differences in last digits of several counters. So the ref files will have to be ammended