Merge provider-kairos CI with kairos

[jimmykarily]

We have lots of duplication between kairos and provider-kairos repositories (e.g. Earthly targets, tests etc). The provider-kairos repository should just be the provider-kairos source code with only a binary as the artifact.

The kairos-io/kairos repository can build provider-kairos images (and core images like it does now) by integrating the provider-kairos binary in the images.

This will allow us to find breaking changes earlier (before we even release kairos core) and also reduce how many CI resources we need.