Figure out how to use Spack v1.0.0

[nkoukpaizan]

Spack is updating the way they handle compiler dependencies. See https://github.com/spack/spack/releases/tag/v1.0.0-alpha.1 and https://github.com/spack/spack/releases/tag/v1.0.0-alpha.4. This is breaking GridKit CI builds (e.g., https://github.com/ORNL/GridKit/actions/runs/14253354329/job/39951067257).

We need to figure out how to update our builds for Spack v1.0.0 and submit issues to spack as needed (there are many many issues being raised by others).
CI is set to use the v0.23.1 Spack buildcache in #76 as a workaround.