Consolidate Product Analytics feature flags

Summary

Now that we're headed towards General Availability with the Product Analytics feature, we need to consolidate feature flags as much as possible as we no longer need to toggle on various pieces of functionality as they're now working together.

Feature flags to consolidate:

• product_analytics_internal_preview
• product_analytics_admin_settings
• project_analytics_dashboards_page

combined_analytics_dashboards should not be considered, as it is the entry point for either Product Analytics' or Optimize's feature set.

The idea is that to enable either group's feature, you would need to enable combined_analytics_dashboards, and then one of the group's feature flags in order to populate the shared dashboard listing.

Proposal

Consolidate all of these flags into product_analytics_dashboards.

It may be easier to rename one of these flags, e.g., product_analytics_internal_preview and re-purpose one of the feature flag roll-out issues.