Active and inactive sublattices

[lbluque]

Summary

Implements another class for inactive sublattices, so that all mcushers have access to both active and inactive sublattices.

• Sublattice and InactiveSublattice as dataclasses.
• Refactored moca.ensemble.sublattice.get_sublattices to become a Processor method.
• all MCUshers now initialized with both active and inactive sublattices.

Checklist

• Code is in the standard Python style.
  Run pycodestyle and flake8
  on your local machine.
• Docstrings have been added in the Google docstring format.
  Run pydocstyle on your code.
• Tests have been added for any new functionality or bug fixes.
• All existing tests pass.