Find audience sizes with telemetry

[tdsmith]

Providing SQL expressions in audience definitions that let us test group memberships will facilitate automatically sizing experiments.

[jaredlockhart]

@tdsmith So is the idea here that we store those queries with the audiences and then some DE jobs will consume this data from here when computing sizing information, so we have it all in one place?

[tdsmith]

Yes, exactly; thanks for filling in that context.

[tdsmith]

@mythmon I think you might have meant to leave that comment on #55.

[mythmon]

That comment is also applicable to #55, but it still fits here. You'll need to export the audiences as a default export from the typescript file for it to work with #43's system.

[tdsmith]

We caught up in Slack; the export default audiences; hiding beneath the diff at the tail of the file is sufficient.