Z-space diagnostics should use the ALE remapping

[adcroft]

The z-space diagnostics are currently using a simple interpolation in the vertical for scalars.

To do:

• Invoke the remapping routines used for ALE to access high-order conservative remapping.
• Transports are already conservatively remapped but could also be made higher-order.

[adcroft]

• Once we are using the remapping toolbox we can and should generalize this code to remap to other spaces (e.g. density).
• We also need find a way to pass through CMOR optional information to z- or rho-space output.