Revert "Merge branch 'revert-6bb61652' into 'master'"

This reverts merge request !3739 (merged), i.e. the revert of !3728 (merged).

The problem with !3728 (merged), namely counters differing, has been understood as an unexpected 'feature' of some counters, where

++m_counter;

and

m_counter += 1;

are not equivalent. Solved by changing the type of counter from a SummingCounter to a BinomialCounter, which is more appropriate for this case.

Must be applied in conjunction with LHCb!4434 (merged)