Updated service account roles in boskos projects (#1363)
Updated service account roles in boskos projects (#1363)

* add script to update the custom role

* add configuration file for custom role, and other changes

* more updates

* clean up

* remove all invalid permissions

* more changes

* grant the gcs service account the role it needs

* no custom role is needed for now

* address feedbacks

* address feedbacks

* address comments

* only tests need storage.admin

* address comments

knative/test-infra,knative/test-infra,knative/test-infra