Cache UCC Docker container

[jordandsullivan]

Is your feature request related to a problem? Please describe.
Currently we have a GitHub Actions workflow for benchmarking which builds the Docker image from scratch every run. This takes time, usually a few minutes.

Describe the solution you'd like
It would be nice to be able to persist a Docker image for a certain period of time, so easiest would be caching layers using GitHub Actions Cache.

Describe alternatives you've considered
If we wanted something more persistent, we could register the UCC container using GitHub Container Registry, Docker Hub, or Amazon ECR (I do not recommend this last one for the reasons explained in #129

Or if philosophically there is some reason folks think we should rebuild every time, we could simply wait the extra time, but I think especially when debugging things unrelated to new versions of the packages installed in the container, it's not necessary to rebuild every single time.
Additional context