v1.9: Add NAS, remove Discover SCU16

[mathomp4]

Description

This PR removes the discover scu16 site as that is not a thing anymore at NCCS. We also add NASA NAS as a new site.

This is based on #1708 so please @climbfuji make sure nothing develop ish came in. I think it's pretty safe.

Dependencies

None

Issues addressed

None

Applications affected

None

Systems affected

Removes NCCS Discover SCU16, adds NASA NAS

cc: @ashley314

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
  • ...

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

[mathomp4]

I am having "issues" with NAS at the moment. For now, I'll undraft just to not keep development stuck. Hopefully by the time 1.9.3 is near final, I'll have figured out why NAS is not happy with me.

[climbfuji]

@mathomp4 Any success with NAS?

[mathomp4]

@mathomp4 Any success with NAS?

@climbfuji Apologies. I was on leave last Thursday and Friday. I'll try this out at NAS tomorrow morning.

[mathomp4]

@mathomp4 Any success with NAS?

@climbfuji Apologies. I was on leave last Thursday and Friday. I'll try this out at NAS tomorrow morning.

Update: I am trying to build now. So far, so good.

[mathomp4]

@climbfuji I think this is now good. I pushed a final update to the README with my "three-step-install" that seems to be working. NAS is slow so it might be late today before the build finishes, but, it looks good.

If not, well, I'll make a "fix GCC build" PR.