feat: Create a builtin module for rpm-ostree

[gmpinder]

We should pull in logic for running the rpm-ostree module into the template. This will allow us to take advantage of using cache mounts to help speed up builds as updating the rpmdb is a slow process during builds.

[xynydev]

Do the cache mounts also provide benefits in CI/CD with ephemeral builders?

[gmpinder]

Do the cache mounts also provide benefits in CI/CD with ephemeral builders?

Unfortunately it would only benefit local builds unless a user had their own runner setup for their repo.

[gmpinder]

Ok so rather than taking over the rpm-ostree module as a whole, the cli is just going to have a cache mount. With how complex the rpm-ostree module could get, I think it would be best to keep it as a script module.