Bump Jenkins Core to 2.401 + Add support for OutputStreamTaskListener

[cyrille-leclerc]

Bump Jenkins Core to 2.401 + Add support for OutputStreamTaskListener

Fix for:

• TeeBuildListener incompatible with OutputStreamTaskListener  #749

Build will pass after merging:

• Remove workaround as Jenkins now better support unit tests of freestyle jobs #780

Testing done

### Submitter checklist
- [ ] Make sure you are opening from a **topic/feature/bugfix branch** (right side) and not your main branch!
- [x] Ensure that the pull request title represents the desired changelog entry
- [x] Please describe what you did
- [ ] Link to relevant issues in GitHub or Jira
- [ ] Link to relevant pull requests, esp. upstream and downstream changes
- [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[kuisathaverat]

related to changes in the workflow plugin jenkinsci/workflow-api-plugin#294 and jenkinsci/workflow-durable-task-step-plugin#323

[cyrille-leclerc]

@kuisathaverat it's ready for review. I can't say we improve the readability of the code. the nuances between BuildListener and TaskListener didn't help us 😄

[kuisathaverat]

I will take a look next week, overall LGTM, but I want to make a manual test of everything.