fix: Appdata test maintenance and pyvista deprecation warning

[koubaa]

Need to use private appdata so that the user's last selection for "ShowTriad" does not affect the test execution.

Also fix an issue where appdata folders were not being deleted by shutil.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.09% (target: -1.00%)	✅ 95.83%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (45a53f6)	2517	2192	87.09%
Head commit (a817889)	2520 (+3)	2197 (+5)	87.18% (+0.09%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1152)	24	23	95.83%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.18%. Comparing base (45a53f6) to head (a817889).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1152      +/-   ##
==========================================
+ Coverage   87.08%   87.18%   +0.09%     
==========================================
  Files          39       39              
  Lines        2517     2520       +3     
==========================================
+ Hits         2192     2197       +5     
+ Misses        325      323       -2     

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