Add namespace id to tier_badge assignment event

Summary

• Add namespace to assignment events for tier_badge experiment. See this comment #345514 (comment 1357925467) and background in that thread.
• We may need to restart experiment(disable/enable feature flag in production) to properly load namespace in the already assigned contexts. Check with @gdoud @p_cordero before restarting.
• Ensure the namespace event being sent is referencing the same namespace that the other tracking events are referencing. It is either going to be source.root_ancestor or project.namespace. It will likely follow this logic. Probably passing this value into the partial would be best.

/cc @eneuberger