Add some detached <-> scheduler edge cases

[yngve-sk]

Issue
Resolves #8896

Approach
At first the job exists as a FAILED job in scheduler: if context is not None and context.has_job_failed(0):, then on the next line it may still be failed, OR (1) set to JobStatus.WAITING, or (2) removed from context.scheduler._jobs, these edge cases are currently not handled, and can occur if we are lucky enough for this change to happen in scheduler between these two lines of code:

            if context is not None and context.has_job_failed(0):
                path = context.job_progress(0).steps[0].std_err_file

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.67%. Comparing base (9817d75) to head (2a90a10).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8898      +/-   ##
==========================================
- Coverage   90.70%   90.67%   -0.03%     
==========================================
  Files         349      349              
  Lines       21776    21776              
==========================================
- Hits        19751    19746       -5     
- Misses       2025     2030       +5     

Flag	Coverage Δ
cli-tests	38.99% <ø> (+<0.01%)	⬆️
gui-tests	71.70% <ø> (ø)
performance-tests	49.24% <ø> (ø)
unit-tests	79.51% <ø> (-0.03%)	⬇️

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[eivindjahren]

I think a few tests should be added for the new behavior and then get this merged as a fix for #8896

[eivindjahren]

👍 (Just need to fix the style workflow)