test/images: bump agnhost to 2.66.1, nginx and glibc-dns-testing

Switch e2e tests to the freshly promoted test images:

- agnhost 2.66.1
- nginx 1.27.0-2 and 1.28.0-2
- glibc-dns-testing 2.1.1

Promoted in kubernetes/k8s.io#9787 and kubernetes/k8s.io#9788.
All four tags verified live on registry.k8s.io with digests
matching the promotion manifests.

The agnhost bump follows build/dependencies.yaml refPaths: the
manifest.go config, the kitten and nautilus BASEIMAGE files, and
the yaml fixtures that hardcode the tag.

Signed-off-by: Davanum Srinivas <davanum@gmail.com>