More portable and reproducible build

[joshkamm]

I'm trying out pixi to try and make the build process no longer rely on custom linux modules and shell scripts that are unique to our HPC cluster environment.

• Get tasks working for the current build system (with the nvidia module already loaded if necessary) and commit that first to make it easier to test with the current system
• Replace env.set.local0 with pixi tasks except for loading nvidia-sdk module
• Replace nvidia-sdk module in pixi task
• Keep athena compilers working with pixi installed compilers
• Add openmpi
• Try pixi verbose option
• Remove extraneous environmental variables
• Get srun command without module load
• Swap globally installed nvc++ for nvcc, then pixi installed nvcc using CXX
• Remove prepended environmental variables to fall back to conda installed libraries to see if pixi can build SlaterGPU on top of its conda dependencies
• Test whether you can write to a variable and use it all under the env section in pixi.toml for a task
• Deal with libcint dependency being hardcoded to a prebuilt filepath on our HPC -> look into rattler-build and or pixi build as a way to build libcint automatically