Data warehouse support for experiments MVP

[danielbachhuber]

Done is:

• Customer should be able to pick a data warehouse table when selecting a goal for an experiment.
• The data warehouse table should be lazily-joined with the events table.
  • TBD whether the customer needs to do this on their own, or whether we should do it for them
  • Probably should validate that the events table is actually lazily-joined.
• We've verified that the expected results are calculated for 'Total count', 'Property value (sum)', and other data warehouse metric aggregations. Any that don't work are hidden.
• Experiments work as expected for Trends queries.
• TBD support for funnels but potentially hide.
• It should be possible to replicate experiment results in an insight. Experiments should link to their corresponding insights.
• Documentation is written/updated.

[danielbachhuber]

Next up:

• Update data warehouse lazy joins to support experiment ASOF LEFT JOIN
• Verify expected results are calculated for 'Property value', etc.
• Explore support for funnels (potentially hide)
• Draft documentation