insights: modify API to take into account frozen insights

Created by: CristinaBirkel

1. Add a new field isFrozen to the InsightView type in the API and make sure it accurately reflects whether or not the insight is frozen, (based on the is_frozen field in insight_view.)
2. When returning insights, do not return any dataSeries data for frozen insights.
3. Other restrictions on the API based on whether or not the user has a Code Insights license:
   • At the very least, any newly created insights should be automatically created with is_frozen=TRUE
   • Consider if it's easy to add in other restrictions, but if not no big deal.