New system class: perlmutter

[slabasan]

Description

• Replace with: A short description of the change, including motivation and context.
• Replace with: A list of any dependencies.
• Replace with: Link(s) to relevant issue(s)
• Complete the checklist for a relevant section(s) below
• Delete sections below that are not relevant to this PR

Adding/modifying a system (docs: Adding a System)

• Add/modify systems/system_name/system.py file
• Add/modify a dry run unit test for system_name in .github/workflows/run.yml
• Add/modify systems/all_hardware_descriptions/hardware_name/hardware_description.yaml which will appear in the docs catalogue

Adding/modifying a benchmark (docs: Adding a Benchmark)

• If modifying the source code of a benchmark: create, self-assign, and link here a follow up issue with a link to the PR in the benchmark repo.
• If package.py upstreamed to Spack is insufficient, add/modify repo/benchmark_name/package.py plus: create, self-assign, and link here a follow up issue with a link to the PR in the Spack repo.
• If application.py upstreamed to Ramble is insufficient, add/modify repo/benchmark_name/application.py plus: create, self-assign, and link here a follow up issue with a link to the PR in the Ramble repo.
• Tags in Ramble's application.py or in repo/benchmark_name/application.py will appear in the docs catalogue
• Add/modify an experiments/benchmark_name/experiment.py to define a single node and multi-node experiments
• Add/modify a dry run unit test in .github/workflows/run.yml

Adding/modifying core functionality, CI, or documentation:

• Update docs
• Update .github/workflows and .gitlab/ci unit tests (if needed)