New System class: Sierra/Lassen

[scheibelp]

This adds a new system definition you can select with benchpark system init to generate a refined version of https://github.com/LLNL/benchpark/tree/develop/configs/LLNL-Sierra-IBM-power9-V100-Infiniband, e.g.

benchpark system init --basedir=test-lassen-create lassen cuda=10-1-243 compiler=xl

The system has two variants:

• one to select CUDA version for components (either 10.1.243 or 11.8.0 for now)
• one to select compiler (4 different options)

The resulting config will contain a single CUDA version, and a compatible compiler selection.

Not all combinations are supported.