Add code coverage for DataGridViewButtonCell

[Zheng-Li01]

Related #13442

Proposed changes

Add unit test file:DataGridViewButtonCellTest.cs for public/protected methods of the DataGridViewButtonCellcs

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 99.04153% with 3 lines in your changes missing coverage. Please review.

Project coverage is 76.74637%. Comparing base (285f3b4) to head (c16278b).
Report is 6 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                  @@
##                main      #13667          +/-   ##
====================================================
- Coverage   97.41503%   76.74637%   -20.66867%     
====================================================
  Files           1192        3256        +2064     
  Lines         353853      641917      +288064     
  Branches        5435       47548       +42113     
====================================================
+ Hits          344706      492648      +147942     
- Misses          8378      145613      +137235     
- Partials         769        3656        +2887     

Flag	Coverage Δ
Debug	76.74637% <99.04153%> (-20.66867%)	⬇️
integration	18.99560% <ø> (?)
production	51.30547% <ø> (?)
test	97.41647% <99.04153%> (+0.00144%)	⬆️
unit	48.68445% <ø> (?)

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[ricardobossan]

Thank you!

[Epica3055]

looks good