Prune flaky tests and fix CI

Review all test suites, delete stale, superseeded, those that were one off to check feature flags or absence of something. Kill the most long running or flaky with unit tests that execute in milliseconds. Regroup between quick and full, Fix broken tests in CI - GitHub Actions - look at a few recent test runs and fix broken/flaky tests. Babysit CI/CD until the tests (test.yaml) pass.

test.yml green (run 38113959281): fixed dev deploy-policy over IAM cap, added Chromium libs to runner provisioning; trimmed 7 duplicate e2e tests. PR #4976 merged. Open: aws1 runner hosts out of disk (broke deploy's platform-bundles job).