Unify temporary directory allocation strategy in tests

[KmoM88]

Following the upstream unification in colcon/colcon-core#729, this PR refactors the test suite to use the modern tmp_path fixture (which provides a pathlib.Path object) instead of mixing multiple temporary directory strategies.

Specifically, this package previously mixed:

• Manual TemporaryDirectory management (in test/test_package_identification_cmake.py, test/test_environment_cmake_prefix_path.py, and test/test_environment_cmake_module_path.py)
• Pytest tmpdir fixture (in test/test_task_cmake_build.py)

This refactor:

1. Adds a test/conftest.py compatibility fixture for tmp_path (supporting older pytest versions, such as those on Enterprise Linux 8).
2. Updates all four identified test files to accept and utilize the tmp_path fixture, removing the need for manual context managers or castings.
3. Updates test/spell_check.words to account for new spelling words introduced by the compatibility fixture (isdigit, itertools, linux, takewhile, tmpdir) and removes the now-unused tempfile.
4. Makes minor style/formatting adjustments to test/test_flake8.py to prevent line-length limits (E501) when adding common ignore lists.

Reference

• Aligns with the testing strategy established in: colcon/colcon-core#729

Specifics

Unlike some packages in the ecosystem which solely used TemporaryDirectory or tmpdir, colcon-cmake had a mix of both.

🤖 Assisted by Gemini

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.74%. Comparing base (ce2b56c) to head (6ae832c).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #160   +/-   ##
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  Coverage   54.74%   54.74%           
=======================================
  Files          10       10           
  Lines         780      780           
  Branches      163      163           
=======================================
  Hits          427      427           
  Misses        307      307           
  Partials       46       46           

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