Describe the bug
Using the spack-managed-x86-64_v3/v1.0 module on Orion & Hercules is problematic because the "pushenv" undoes spack-stack's changes to $MODULEPATH, making our stack-oneapi module unable to load. For now on Orion, I've modified /apps/contrib/spack-stack/spack-stack-1.9.0/envs/ue-oneapi-2024.2.1/install/modulefiles/oneapi/2024.2.1/stack-intel-oneapi-mpi/2021.13.lua and /apps/contrib/spack-stack/spack-stack-1.9.0/envs/ue-oneapi-2024.2.1/install/modulefiles/Core/stack-oneapi/2024.2.1.lua to prepend $MODULEPATH using the same set of paths that would have come from spack-managed-x86-64_v3/v1.0, and this seems to work. We should bake the modified MODULEPATH into the site configs.