feat: debug testing

[germa89]

Description

Now using the envvar PYMAPDL_DEBUG_TESTING, we can produce more logs while testing.

Issue linked

Related to #3347 but for testing only

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 87.01%. Comparing base (1473bdd) to head (6f7e0eb).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3594      +/-   ##
==========================================
+ Coverage   86.97%   87.01%   +0.03%     
==========================================
  Files         187      187              
  Lines       14630    14661      +31     
==========================================
+ Hits        12725    12757      +32     
+ Misses       1905     1904       -1