[Feature] Docker Image improvements

[philosowaffle]

https://www.augmentedmind.de/2022/02/20/optimize-docker-image-security/

[philosowaffle]

https://contains.dev/blog/mastering-docker-cache

[philosowaffle]

Regarding non-root and mounted volume permissions: https://stackoverflow.com/questions/39397548/how-to-give-non-root-user-in-docker-container-access-to-a-volume-mounted-on-the

Regarding security of using runuser: https://stackoverflow.com/questions/65574334/docker-is-it-safe-to-switch-to-non-root-user-in-entrypoint

[philosowaffle]

Summary of changes:

1. Docker image now builds in ~2min instead of 11min. due to layer caching improvements
2. While the container itself still runs as root, the process no longer runs as root, this helps mitigate the risk of a security hole in the P2G process allowing a bad actor to break out into an environment where it has root access.