feat: distribution is a dict and nodes and cluster are top level

[onedr0p]

Hopefully this will be the last refactoring of the config options, it's really hard to come up with something that meets my expectations and is easy for people to follow.

• Makes distribution a dict which will allow for talos/k0s/k3s specific configurations

  distribution:
    type: talos
    talos: {}

• nodes and cluster are each back to top level config

• .mjfilter.py files now defaults if keys are not present

• Defaults nodes.dns_servers to 1.1.1.1 and 1.0.0.1

• Offloads some README items to the configuration file.