Avoid publishing empty timer metrics to Datadog

A Code Wizzard timer is generating 16 custom metrics in Datadog: min, max, percentiles, count, sum, rates ...

There is a expansion filter to limit the number of metrics per timer (9 with default filter and 6 with minimal filter) but this is still too much if the timer is empty because nothing was measured so far.

The idea is to introduce an option to report empty timer as a counter with a value of 0, this will saves up to 15 custom metrics when the timer is not used.

To avoid any regression, this option needs to be explicitly activated with

metrics.datadog.emptyTimerAsCount=true