CHORE: Enforce ruff pyflakes F rules

[ecoussoux-ansys]

Description

This PR is a follow-up to #6157, which introduced a minimal configuration for ruff to pyaedt and to #6203, which applied the "E" rules (related to pycodestyle) on the entire codebase.
Here, the "F" rules (related to Pyflakes, see https://docs.astral.sh/ruff/rules/#pyflakes-f) are enforced, allowing their removal from the list of ignored linting rules for ruff.

This effort is part of the migration of pyaedt towards using ruff for code formatting and linting, as requested in issue #4775.
This PR is also contributing to the efforts described in issue #5504.

"F" rules were incrementally applied (one rule per commit) using the same approach as in #6203.
The strategy followed for enforcing this set of rules has been to avoid as much as possible the deactivation of specific checks on a per-file basis and the creation of special cases. This has occasionally involved introducing some debatable changes, which reviewers might want to pay particular attention to: These are listed below, together with other non-trivial modifications suggested in this PR:

• The approach for fixing errors related to rule F401 (unused-import) in __init__.py files was to follow one of the methods described in https://docs.astral.sh/ruff/rules/unused-import/, which consists in explicitly declaring the imported symbols as part of the modules' interfaces using __all__. Some instances of in-file noqa: F401 were also removed where possible,
• A refactoring of the imports in src/ansys/aedt/core/__init__.py was applied, so that variables and classes are directly imported from the modules in which these are defined,
• Rule F403 (undefined-local-with-import-star) only impacted files in the src/pyaedt/ folder. Therefore, it was decided to ignore this rule for all files from this folder in order not to invest time in tedious refactoring of this deprecated part of the codebase,
• Rule F821 (undefined-name) is ignored in file doc/source/Resources/pyaedt_installer_from_aedt.py for lack of a better alternative for managing variables specific to IronPython with respect to this rule,
• The test test_plot_insertion_losses in test_touchstone_data.py was modified. Currently the variable res returned line 32 is equal to []: res is not []returns True but the syntax res != [] recommended by ruff will return False. Therefore, the asserted equality is rewritten to res == [], in line with the result actually obtained from this test, despite it seeming to contradict the previous implementation for this check,
• The ruff pre-commit hook is updated in .pre-commit-config.yaml.

Issue linked

Related to #4775 and #5504.

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[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 85.29%. Comparing base (0e05f78) to head (9ce27d7).

❌ Your patch check has failed because the patch coverage (80.00%) is below the target coverage (85.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6239   +/-   ##
=======================================
  Coverage   85.29%   85.29%           
=======================================
  Files         173      173           
  Lines       65310    65273   -37     
=======================================
- Hits        55705    55677   -28     
+ Misses       9605     9596    -9     

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[SMoraisAnsys]

Thanks for the changes @ecoussoux-ansys !!!
I left some comments. I'm wondering if some of the changes are due to ruff or if they are changes performed in the main branch and somehow reflected in this PR. Can you have a look and address them ?