Ability to push bundles to OCI registries

[cohix]

Adding a subo push and/or subo pull which packages the bundle as an OCI image and then pushes it to an image registry would be very useful.

Atmo could also be directed to use an image from a registry.

We can take inspiration from wasm-to-oci, though it will be different as we're pushing a bundle, not a single Wasm module.

[zhangwinning]

Hi @cohix, I want to try to solve this problem.

[cohix]

@zhangwinning please feel free! Let me know if you have any questions.