Add participation metrics to workspace

[#1]

In Ad Hoc Analytics it's possible to use participation metrics.

This is something that we often use.

In workspace this metric doesn't exist.

Its possible to get the same results by creating a segment but having the metric would be easier.

[#2]

Try right-clicking the metric in a Freeform table, then enabling 'non-default attribution model':

Or enabling Participation via Calc Metrics: