Add lint test to check existence of test profile

[fa2k]

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

This is the first part of #1837.

See below comment: The following is no longer true (no way to "strike through" in github?):
It is not an ideal implementation, because it has to call nextflow, and only gets indirect indication of the failure due to the exit code. If there's a better way to reliably parse the config with python, I will use that instead- I hope someone can offer guidance on that if possible.

This is a draft PR, not ready for merge.

[fa2k]

The test is now parsing nextflow.config to verify the existence of the test profile. It's failing one CI test and I don't know why. I'm going to change it to not be a draft.

[codecov]

Codecov Report

Merging #2478 (c57cb8c) into dev (9171fa0) will decrease coverage by 0.08%.
Report is 7 commits behind head on dev.
The diff coverage is 95.23%.

❗ Current head c57cb8c differs from pull request most recent head 9457021. Consider uploading reports for the commit 9457021 to get more accurate results

@@            Coverage Diff             @@
##              dev    #2478      +/-   ##
==========================================
- Coverage   70.71%   70.63%   -0.08%     
==========================================
  Files          87       87              
  Lines        9424     9461      +37     
==========================================
+ Hits         6664     6683      +19     
- Misses       2760     2778      +18     

Files	Coverage Δ
nf_core/lint/actions_ci.py	82.85% <ø> (ø)
nf_core/lint/nextflow_config.py	80.48% <95.23%> (+3.03%)	⬆️

... and 7 files with indirect coverage changes

[mashehu]

we added a new type checker for python code, which unfortunately is still a bit too aggressive. you can ignore that specific test for now.