FIX: Add all PyAEDT Extension tests

[Samuelopez-ansys]

This pull request updates the continuous integration workflow to expand test coverage for the external/pyaedt extensions. The main change is the addition of several new system-level tests to the CI pipeline, which will help catch issues earlier and improve overall code quality.

Testing improvements:

• Added the following system tests to the ci-release.yml workflow: test_export_to_3d.py, test_export_layout.py, test_post_layout_design.py, and test_via_clustering.py in the external/pyaedt/tests/system/extensions/ directory.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.84%. Comparing base (5cbae21) to head (2dfeb6c).
⚠️ Report is 43 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1949      +/-   ##
==========================================
+ Coverage   70.20%   70.84%   +0.63%     
==========================================
  Files         261      263       +2     
  Lines       42416    42876     +460     
==========================================
+ Hits        29779    30376     +597     
+ Misses      12637    12500     -137     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[SMoraisAnsys]

LGTM, please @hui-zhou-a and @svandenb-dev could you ensure that you cover the pyaedt tests involving pyedb when releasing ? It's not the first time that a new release of pyedb is breaking pyaedt's CI :/

[svandenb-dev]

LGTM