[WIP] Various updates in RADIUSS Spack Configs

[adrienbernede]

Changes to RSC:

• Spack environments split in separate files so that users can access packages.yaml and compilers.yaml directly
• Update externals, add new externals to support building other projects (axom)
• Make sure we do not reuse specs already installed (concretization is not influenced by what's already built)
• Update rocm tioga toolchain

Changes to Shared CI:

• Update with improved job command handling

Other changes:

• Export host config as artifacts

[rhornung67]

@adrienbernede if you merge https://github.com/LLNL/RAJAPerf/tree/task/rhornung67/new-sycl into https://github.com/LLNL/RAJAPerf/tree/woptim/rsc-update (the branch for this PR), you should be able to update the corona SYCL build to the clang20 version. Then, I believe the build and tests should pass.

Please let me know if it works or if you hit any issues.

[adrienbernede]

@rhornung67 That worked seamlessly!

[rhornung67]

@adrienbernede Let me know when the rsc-update PRs are ready to merge and I will approve.