JMH: SingleShot mode should handle OperationsPerInvocations > 1

There seems to be a corner case in SingleShot mode handling: while the internal code handles OperationsPerInvocations > 1 for e.g. profilers normalization with BenchmarkTaskResult, OPI > 1 does not affect the score.

Unfortunately, the fix involves modifying a constructor in SingleShotResult, which raises a minor compatibility question. We can side-step it for a while by adding the constructor overload.