Investigate GHCR

[johnSchnake]

We've always pushed images to Dockerhub but ran into rate limiting issues, usually in CI systems.

Then we moved to also supporting an internal, VMware Harbor instance which avoids the rate limit issue but required you to manually specify the location for sonobuoy/systemd-logs images.

I didnt realize it until today, but as part of the vmware-tanzu org, we have access to the enterprise level of Github Container Registry. Using this would:

• continue to use OSS standard tools
• avoid using a Harbor instance which outside contributors can't push to (if we ever had outside maintainers)
• avoid the rate limit issue

I think this is a win to start publishing there and use it by default which would also fix #1680