[Release/9.0] Fix false-positive WinForms Analyzer diagnostics.

[KlausLoeffelmann]

Fixes #13160.
We're servicing only the false-positive WinForms Analyzers edge cases for low-risk servicing.

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 41.66667% with 14 lines in your changes missing coverage. Please review.

Project coverage is 74.83965%. Comparing base (4a9a9f0) to head (133e570).
Report is 6 commits behind head on release/9.0.

Additional details and impacted files

@@                  Coverage Diff                   @@
##           release/9.0      #13411          +/-   ##
======================================================
+ Coverage     44.90473%   74.83965%   +29.93492%     
======================================================
  Files             1956        3022        +1066     
  Lines           284391      630480      +346089     
  Branches         41754       46806        +5052     
======================================================
+ Hits            127705      471849      +344144     
- Misses          149047      155242        +6195     
+ Partials          7639        3389        -4250     

Flag	Coverage Δ
Debug	74.83965% <41.66667%> (+29.93492%)	⬆️
integration	18.02233% <ø> (?)
production	47.87435% <41.66667%> (+2.96961%)	⬆️
test	97.00005% <ø> (?)
unit	44.90677% <41.66667%> (+0.00204%)	⬆️

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[Tanya-Solyanik]

Thank you!