Clear cached functions on every test

[Schamper]

After we enabled test randomization, sometimes we get a test failure ontests/tools/test_query.py::test_invalid_functions and tests/tools/test_query.py::test_invalid_excluded_functions (https://github.com/fox-it/dissect.target/actions/runs/14494203513/job/40657657729?pr=1108)

However, I can't reproduce even with the same seed. I have a suspicion that a cached _generate_long_paths is the issue, so I moved the clearing of that cache from just the test_plugin.py file to every test in the suite.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.01%. Comparing base (8fb5b03) to head (8f8ea10).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1110   +/-   ##
=======================================
  Coverage   78.01%   78.01%           
=======================================
  Files         354      354           
  Lines       32049    32049           
=======================================
  Hits        25003    25003           
  Misses       7046     7046           

Flag	Coverage Δ
unittests	78.01% <ø> (ø)

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