Stricter Dask tests cleanup

[ogrisel]

On my laptop, running the latest version of dask and distributed, with tests that run in a random order for some reason,

• the cleanup fixture (dependency of the loop fixture) would be not found by pytest (see Can't find cleanup pytest fixture dask/dask#9137),
• tests executed after test_joblib_warning_inside_dask_daemonic_worker would either fail or error at teardown because of non-collected subprocess workers from that test.

[ogrisel]

Hopefully this will fix errors such as:

________________________ ERROR at setup of test_simple _________________________
file /home/runner/work/cloudpickle/joblib/joblib/test/test_dask.py, line 42
  def test_simple(loop):
file /opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/distributed/utils_test.py, line 127
  @pytest.fixture
  def loop(loop_in_thread):
file /opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/distributed/utils_test.py, line 132
  @pytest.fixture
  def loop_in_thread(cleanup):
E       fixture 'cleanup' not found
>       available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, loop, loop_in_thread, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

observed in:

https://github.com/cloudpipe/cloudpickle/actions/runs/6485430661/job/17611486887?pr=519

from cloudpipe/cloudpickle#519

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (2ce6282) 95.00% compared to head (b8bbb3c) 95.02%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1514      +/-   ##
==========================================
+ Coverage   95.00%   95.02%   +0.01%     
==========================================
  Files          45       45              
  Lines        7550     7553       +3     
==========================================
+ Hits         7173     7177       +4     
+ Misses        377      376       -1     

Files	Coverage Δ
joblib/test/test_dask.py	92.33% <100.00%> (+1.13%)	⬆️

... and 5 files with indirect coverage changes

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[ogrisel]

The 2 distributed runs pass. I will merge without waiting for the scikit-learn tests to be able to iterate faster on the cloudpickle CI.