wgrib2: support variants ipolates and netcdf

[rickgrubin-noaa]

Description

Add support for variants ipolates and netcdf for release/1.9.0 (and expected tag 1.9.3) for wgrib2@3.6.0

Will require reverting changes to .gitmodules prior to merging.

Dependencies

• waiting on Support variant netcdf when=@3.6: spack#561

Issues addressed

Resolves #1685
Resolves #1711

Applications affected

Any application that builds with / links against wgrib2@3.6.0 with variants ipolates and / or netcdf

Systems affected

Any system that specs wgrib2@3.6.0 with variants ipolates and / or netcdf

Testing

• CI: Note whether the automatic tests (GitHub actions tests that run automatically for every commit) pass or not
  • GitHub actions CI tests pass
  • GitHub actions CI tests do not pass (provide explanation)
  • GitHub actions CI tests skipped (provide explanation if necessary)
• New tests added: List and describe any new tests added to GitHub actions
  • ...
• Additional testing: Add information on any additional tests conducted
  • see attached files: spack.yaml, log.concretize, and excerpted log.install

Checklist

• This PR addresses one issue/problem/enhancement or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.
• All necessary updates to the documentation on readthedocs are included in this PR
  • For site config updates, check in particular doc/source/PreConfiguredSites.rst and doc/source/MaintainersSection.rst
• All necessary updates to the spack-stack wiki will be made when this PR is merged

[rickgrubin-noaa]

log.concretize.txt
log.install.txt
spack.yaml.txt

[climbfuji]

I don't see the submodule pointer update for spack (new head of release/1.9.0)