Pull through container registry cache for demo

Nobody has claimed this yet.

**Describe the solution you'd like:**
Currently, when provisioning a cluster the containers required are pulled down for every node which increases the provisioning time. It would be worth us using a container registry that support pull through caching. We can then configure containerd on the microvm nodes to use this registry as a cache.

It would be worth looking at:

- [Harbor](https://github.com/goharbor/harbor/blob/master/contrib/Configure_mirror.md)
- [Docker Registry](https://docs.docker.com/registry/recipes/mirror/)

We could also look at a HTTP proxy cache such as Envoy, HAProxy

**Why do you want this feature:**

To speed up provisioning of nodes.

**Anything else you would like to add:**
[Miscellaneous information that will assist in solving the issue.]

Review the linked Harbor and Docker Registry mirror references, then inspect the cluster provisioning path and containerd configuration on the microVM nodes. Compare the registry-cache and HTTP-proxy options; done means node image pulls use the cache during provisioning and provisioning time is reduced.

Written by the indexing model from the issue text.