Change default pole_method when source grid does bounds do not include the pole

[stephenworsley]

✨ Feature Request

When the source grid covers a limited band of latitudes, and especially when both bounds are the same side of the equator, it's likely to be inappropriate to extrapolate values that lie outside the source domain. The default behaviour for bilinear and nearest neighbour regridding is to use the esmpy ploe_method ALLAVG, however in such cases a it would be more appropriate to use the method NONE.