Rename Greenland Regions --> ISMIP6 Greenland Regions

[xylar]

This merge requires geometric_features 1.6.0, where a breaking change was made that renamed Greenland Regions to ISMIP6 Greenland Regions for clarity. (NASA Greenland Regions were also added.)

This merge also fixes an issue with the docs in which the intersphinx link to MPAS-Tools is corrected (stable --> master).

Checklist

• Testing comment in the PR documents testing used to verify the changes

[xylar]

Testing

I ran the test suite on Chrysalis:
https://web.lcrc.anl.gov/public/e3sm/diagnostic_output/ac.xasay-davis/analysis_testing/chrysalis/rename-greenland-regions/
Because the web portal is glitching, I couldn't check all the output but I was able to verify that Greenland Regions were plotting as expected in the main_py3.11 test and that the documentation looked right. All tests finished as expected.