Several fixes to global ocean meshes with MALI topography

[xylar]

This merge:

• Fixes MALI ice draft calculation for grounded ice. The ice draft is determined by flotation in floating regions but is equal to the bed elevation in grounded regions. We also include sea_level (currently zero) in the calculation of the ice draft.
• Fixes renormalization of MALI topography. It is first masked to below sea level, then remapped, then renormalized by the ocean fraction (area below sea level).
• Uses the correct target scrip file for topo remapping. We need to use the appropriate unsmoothed or smoothed scrip file, whereas we were previously creating a new MPAS-Ocean scrip file that was always without smoothing.

Checklist

• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[xylar]

Testing

I ran the ocean/global_ocean/SOwISC12to30/MALI_topo_AIS_4to20km/mesh test case after:

• setting ocean_includes_grounded=True in two places in compass/ocean/tests/global_ocean/mesh/__init__.py
• setting expand_factor = 2 in mesh.cfg

I now see, as expected:

• the draft is exactly equal to the bed both before and after remapping of the MALI topography in fully grounded regions
• the draft is never below the bed (the water column thickness is non-negative)
• the MALI topography is masked by oceanFrac = bed < 0, as expected
• the remapped MALI topography is renormalized by the remapped oceanFrac as expected: The topography does not drop toward zero at locations where oceanFrac < 1
• the remapped MALI topography in the remap_topo_smoothed step is, in fact, visibly smoother than the remapped topography in the unsmoothed step.
• the combined topography doesn't show any visible jumps at the boundary where landIceFraction has fractional values (used to interpolate between the two topography deatasets)
• the culled mesh removes masked areas of zero bathymetry and ice draft (locations where bathymetry was above sea level before masking)
• on the culled mesh, the 0.27 < oceanFracObserved < 1; areas where oceanFracObserved < 0.5 are few and likely are explained by topological requirements (e.g. adding cells to the ocean to prevent isolated vertices)

For paraview verification, see xdmf files in:

/lcrc/group/e3sm/ac.xylar/compass_1.9/chrysalis/test_20260113/fix-mali-draft-with-smoothing3/ocean/global_ocean/SOwISC12to30/MALI_topo_AIS_4to20km/mesh/*/xdmf_*/

[xylar]

@cbegeman, could you take a look at this when you have time? It likely makes sense to rebase #931 onto this branch.