for new sp impl, unify naming/semantics/theme

[mahf708]

Makani does:

        if isinstance(self.inverse_transform, thd.DistributedInverseRealSHT):
            self.modes_lat_local = self.inverse_transform.l_shapes[comm.get_rank("h")]
            self.modes_lon_local = self.inverse_transform.m_shapes[comm.get_rank("w")]
            self.nlat_local = self.inverse_transform.lat_shapes[comm.get_rank("h")]
            self.nlon_local = self.inverse_transform.lon_shapes[comm.get_rank("w")]
        else:
            self.modes_lat_local = self.modes_lat
            self.modes_lon_local = self.modes_lon
            self.nlat_local = self.inverse_transform.nlat
            self.nlon_local = self.inverse_transform.nlon

I don't mind you keeping what you have here instead, it seems clear/obvious enough. Or maybe better is to revert this for now and store the full weight shape.

Originally posted by @mcgibbon in #900 (comment)