Real-data pytests

[WardDeb]

This PR initiates 'real data' tests. In brief:

• Bumped all checkouts to V4
• split up pytests from linux.yml
• action runs mRNA-seq wf on subsetted fq file (included in the repo).

[WardDeb]

Hey Ward,

am I reading this right that all of the build tests would be replaced by testing the mRNA-seq workflow only?

Best, Katarzyna

No, the build tests remain as they were before. The pytests are moved into a separate action and now consist of:

• jobcount dryruns (as they were before).
• true run with real data (implemented in this PR).