Add unit test for DateTimePicker 6 events

[John-Qiao]

related #10453

Proposed changes

• Add unit tests for below 6 events

1. BackgroundImageLayoutChanged
2. Click
3. DoubleClick
4. ForeColorChanged
5. PaddingChanged
6. TextChanged

Customer Impact

• None

Regression?

• No

Risk

• Minimal

Screenshots

Before

After

Test methodology

• Unit tests

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.23047%. Comparing base (9a9d4a2) to head (6eeaea2).
Report is 36 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #11318         +/-   ##
===================================================
- Coverage   74.30944%   74.23047%   -0.07897%     
===================================================
  Files           3018        3021          +3     
  Lines         626230      626255         +25     
  Branches       46599       46698         +99     
===================================================
- Hits          465348      464872        -476     
- Misses        157479      157986        +507     
+ Partials        3403        3397          -6     

Flag	Coverage Δ
Debug	74.23047% <100.00000%> (-0.07897%)	⬇️
integration	18.26780% <ø> (-0.03729%)	⬇️
production	46.88713% <ø> (-0.06046%)	⬇️
test	97.03957% <100.00000%> (-0.00074%)	⬇️
unit	43.84344% <ø> (-0.05278%)	⬇️

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[ricardobossan]

LGTM

[lonitra]

Thank you