Parallelize wfmash

[subwaystation]

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
  • If you've added a new tool - add to the software_versions process and a regex to scrape_software_versions.py
  • If you've added a new tool - have you followed the pipeline conventions in the contribution docs
  • If necessary, also make a PR on the nf-core/pangenome branch on the nf-core/test-datasets repository.
• Make sure your code lints (nf-core lint .).
• Ensure the test suite passes (nextflow run . -profile test,docker).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

This PR parallelizes the wfmash process so it can scale on a whole cluster. This is possible with the https://github.com/ekg/wfmash/blob/master/scripts/split_approx_mappings_in_chunks.py script thanks to @AndreaGuarracino!

• Added process wfmashMap which only runs the approximate mapping step of wfmash.
• Added process splitApproxMappingsInChunks which divides the approximate .paf into chunks of equal problem size.
• Added process wfmashAlign which performs the base-level alignment step of wfmash for each chunk in parallel process submissions.
• The --wfmash_only parameter stops the pipeline after the wfmash step. This makes it possible for user to scale only wfmash across a whole cluster.
• Updated tests, JSON schemas, etc.

[subwaystation]

As expected, only the nf-core linting is failing. Ready to merge :)