Docker executes as root

[paulhauner]

Description

The Dockerfile in the root currently uses the root user to run lighthouse. This is not best-practice.

It's going to hurt users to migrate across, but I think it's worth doing and worth doing before mainnet.

We will also need to ensure https://github.com/sigp/lighthouse-docker is fine with this change, too.

[hukkin]

Made the change to Dockerfile in #2021 and sigp/lighthouse-docker#47 should make lighthouse-docker compatible too.

[zx8]

Is there any chance we could get this resolved?

Lighthouse was just flagged as one of the only containers we are running as root in a recent security audit, and we'd really prefer not to have to run a fork to fix it ourselves. 🙏

I understand the backwards-compatibility concern, so perhaps in the interim you could provide a separate tag which runs as non-root, and people like ourselves can use that tag until this is addressed in a more formal way? I'd really hate to have to diverge from the official upstream image for an issue this trivial.