Quite a few images are only used a few times in a few tests. Thus,
the images are being centralized into the agnhost image, reducing
the number of images that have to be pulled and used.
This PR replaces the usage of the following images with agnhost:
- audit-proxy
- crd-conversion-webhook
- entrypoint-tester
- inclusterclient
- iperf
- porter
- serve-hostname
This is part of the transition to using framework/log instead
of the Logf inside the framework package. This will help with
import size/cycles when importing the framework or subpackages.
**What this PR does / why we need it:** This PR adds [sig-auth] prefix to
workload e2e tests in accord to requirements of adding a SIG dashboard
to testgrid. Refer PR #48781 for guidelines.
