[WIP] Allocation implementation for mpibind modifier

[august-knox]

Description

Alternative implementation for mpibind(#608), moving all mpi-command editing to the allocation modifier, where this already takes place by default. Functionality remains the same.
Example command:
benchpark experiment init --dest=saxpy saxpy mpibind=v +openmp

So far, modes include: off, on, v, vv, greedy:0

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

• (optional) If package upstreamed to Spack is insufficient, add/modify repo/benchmark_name/package.py
• (optional) If application upstreamed to Ramble is insufficient, add/modify repo/benchmark_name/application.py
• 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