Extract coordinate transformation code from agActor to pfs_utils

INSTRM-2565 will transform the pfsConfig guidestar coordaintes to apply proper motion and other telescope transformations, but currently that code is tightly coupled with the catalog-matching code inside agActor. The coordinate transformation code should be extracted and moved to pfs_utils.coordinates and the other various transformation methods already in pfs_utils.coordinates should be marked as deprecated or have their usage-needs explicitly stated in the docstrings.