add config for frecency experiment

[jaredsnyder]

Doc: https://docs.google.com/document/d/1gJfx8ITCwBOuy2BiRux_fATgAYW1UxZicAbIcYFdNJc/edit?tab=t.erl2a62ns55c

[jaredsnyder]

Jetstream preview dashboard: https://mozilla.cloud.looker.com/dashboards/experimentation::jetstream_preview?Project=mozdata&Parameter=null&Slug=frecency_based_sponsored_tiles_poc&Dataset=tmp&Analysis+Period=daily&Analysis+Basis=enrollments&Metric=&Statistic=&Segment=all&Comparison=NULL

[mikewilli]

I left one specific comment on a change I know you'll need. There are some other issues here that you'll likely be able to find yourself and fix once jetstream preview is fixed in mozilla/jetstream#2936, but the problem is with the total_tile_third* and sponsored_tile* metrics -- metric-config-parser is saying some of them are missing statistics.

[mikewilli]

For posterity:

As far as @jaredsnyder and I could tell, the order in which metrics were defined in the daily/weekly/overall lists made a difference in whether the config resolved properly (see this commit), at least for the metrics that depend on others. This appears to be because the parser just pulls in and resolves the metrics in the order they're defined, and so if the downstream metric is in the list before its dependencies, those dependent metrics don't exist as far as the parser knows.

I also filed this ticket #1295