Activator clean up items #425
Description
- set runner name
- be consistent in build command and container paths across dockerfiles
- reuse more of IGW infra (e.g., ext_proc runner, health, ...) once refactored
- disable direct scale up/down - delegated to autoscaler (Activiator should only buffer request and signal autoscaler on scale-from-zero)
Followup on comments from #387 captured in issue to avoid blocking initial merge for experimentation