Generalize and cleanup Spack package

[white238]

We should do some work to cleanup our project's Spack package in an effort to push it up to Spack's repository.

Things we should do that I can think off off the top of my head

1. Remove optional variants and versions for dependencies
2. Add conflicts for known bad versions (for example, sundials@:6.0.0)
3. Remove debug/release build type or guard it with a note not to push it up
4. Review optional dependencies that we haven't actually tested
5. Add our package to the Spack CI tests
6. Change debug variant to just use the base CachedCMakePackage variant build_type

[chapman39]

What would step 5 involve? Moving our package to spack builtin?

I think besides step 5, this issue is resolved.