Add an e2e test for RPS based autoscaling (#5244)
Add an e2e test for RPS based autoscaling (#5244)

* add test

* use vegeta

* add target tu as annotations

* remove ctx settings

* consider resolvedDomain

* solve comments

* use map for easy extention

* address comment

* add client side concurrency

* add hpa

* fix string

* remove client requests

* change error msg

* add a TODO

knative/serving,knative/serving