Add nf-test to pipeline template CI workflow

[adamrtalbot]

Will close #2854

Replaces CI workflow with nf-test version.

Changes:

• Uses a Python script to find changed files between PR branch and base.
• Flags any nf-test files present
• Adds 'special' cases such as pipeline level tests
• Identifies any dependencies of changed tests
• Returns as list of nf-test files to run
• Runs nf-test as a matrix over those files
• Confirm pass based on results of previous

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

[adamrtalbot]

@nf-core-bot changelog

[mashehu]

first, we need docs on how to write nf-test for pipelines

[adamrtalbot]

first, we need docs on how to write nf-test for pipelines

And I think this would make more sense with a test added to the pipeline.

[mirpedrol]

We should also add nf-test to the pipieline template, the current template doesn't have them, so this won't work with most of the pipelines which don't have nf-test.