Support a mode where Condition Sets emit the underlying telemetry value when true

[akhenry]

Is your feature request related to a problem? Please describe.

Current condition sets can emit one of a finite set of discrete values, depending on which condition is true.
For some use cases, it would be useful to have condition sets emit the matching telemetry value from the underlying telemetry object when matched, and nothing if now.

This would, in effect, allow condition sets to be used as a filter.