refactor: using test classes in test_inline tests

[germa89]

Description

As the title.

Using:

hyperfine --warmup 2 --show-output "pytest tests/test_inline_functions/*"

Performance

Before

  Time (mean ± σ):     53.528 s ±  3.060 s    [User: 3.689 s, System: 1.806 s]
  Range (min … max):   48.600 s … 58.802 s    10 runs

After

  Time (mean ± σ):     43.933 s ±  4.528 s    [User: 3.644 s, System: 1.557 s]
  Range (min … max):   39.058 s … 52.305 s    10 runs

Issue linked

NA

Checklist

• I have visited and read Develop PyMAPDL.
• I have tested my changes locally
• I have added necessary documentation or updated existing documentation.
• I have followed the PyMAPDL coding style guidelines.
• I have added appropriate unit tests that also ensure the minimal coverage criteria.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have marked this PR as draft if it is not ready to be reviewed yet.
• I have made sure that the title of my PR follows Commit naming conventions (e.g. feat: adding new MAPDL command)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.35%. Comparing base (e63570e) to head (2da243e).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3524      +/-   ##
==========================================
- Coverage   82.40%   82.35%   -0.05%     
==========================================
  Files          58       58              
  Lines       10017    10017              
==========================================
- Hits         8255     8250       -5     
- Misses       1762     1767       +5     

[germa89]

@pyansys-ci-bot LGTM.

[pyansys-ci-bot]

✅ Approving this PR because germa89 said so in here 😬