feat: build nvidia images in main repo

[bsherman]

This adds the nvidia build scripts to the repo and reconfigures Containerfile to build both FOO-main and FOO-nvidia images per matrix provided build-args. Workflow matrix was modified to support this use case, including changes to variables and tag generation.

Reviewers: please double-check the generated tags look correct per image. I did review and put some effort into this, but would appreciate extra eyes.

Changes which were not technically required:

• "main" build.sh, post-install.sh, packages.json renamed (with main- prefix) to make things more consistent and easier to follow for future
• switched to COPY instead of ADD in Containerfile for compliance with best practices
• added retry logic to curl in github-release-install.sh to avoid some observed intermittent errors

[bsherman]

After merging, we must disable actions on the https://github.com/ublue-os/nvidia/ repo, and probably post a message to the README and/or archive the repo.

[castrojo]

iirc archiving the repo will turn off the actions in one step.

[bsherman]

iirc archiving the repo will turn off the actions in one step.

Yes but do we want a message on the readme or no?

[castrojo]

Yeah, a signpost would help, I can work on that. You keep going on this.

[bsherman]

You keep going on this.

I already added main repo as "Admin" to the container packages (*-nvidia) so the pushes should succeed.

I think this is ready as soon as y'all approve.

[p5]

LGTM 🤞

[p5]

(Unrelated)
It might be a good idea to bundle these Nvidia install and post-install scripts into the akmods image instead of requiring downstream consumers to copy, paste and keep them maintained.

We can keep them up-to-date in the akmods repo, then if people are consuming the akmods repo rather than main images, they have the scripts bundled with the image to call.