Fix E2E namespace to headlamp-dev and add RBAC manifest

- Changed E2E_NAMESPACE from privilegedescalation-dev to headlamp-dev
  in e2e.yaml, deploy-e2e-headlamp.sh, and teardown-e2e-headlamp.sh
- Added deployment/e2e-ci-runner-rbac.yaml (copy from polaris repo)
- The ARC runner SA has RBAC scoped to headlamp-dev, not
  privilegedescalation-dev — this caused E2E run failures.

- PRI-619 QA review feedback from Regina

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/e2e.yaml

@@ -15,7 +15,7 @@ concurrency:
   cancel-in-progress: false
 
 env:
-  E2E_NAMESPACE: privilegedescalation-dev
+  E2E_NAMESPACE: headlamp-dev
   E2E_RELEASE: headlamp-e2e
   HEADLAMP_VERSION: v0.40.1