E2E: tighten anonymous ACL policy

[tgross]

Our E2E environment uses a broad anonymous ACL policy, with the expectation that tests that need tighter restrictions will opt-in to more restrictive policies. Unfortunately this makes bugs like #16470 easier to miss. We should probably remove the anonymous policy (or make it extremely restrictive) and then require that tests set up any policies they need. The root test runner is using a management token anyways.