move to coder/images

[matifali]

I am unfamiliar with why these images are called enterprise-xxx. We should probably rename the repo and images to coder/images.
We can keep the legacy images on dockerhub and publish the new ones ghcr.io

The idea is to have something like coder/modules and coder/templates and integrate with https://registry.coder.com where we can list images too. We can also accept community contributions for templates and images as we do with modules and list on our registry.

cc: @bpmct

[johnstcn]

While we're at it, I'd like to change the naming scheme:

• images/base/ubuntu.Dockerfile -> ubuntu:base
• images/minimal/ubuntu.Dockerfile -> ubuntu:minimal
• images/$IMAGE/$DISTRO.Dockerfile -> $DISTRO:$IMAGE

This might entail some shuffling things around on-disk.