[release/9.0] fix #13305 Baseline SnapLines do not appear in DesignSurface

[github-actions]

Backport of #13324 to release/9.0

The cause of this issue

This issue is caused by PR10279

These are two of all changes make in PR10279

BehaviorService, DragAssistanceManager use SnapLines to add some effects during design time.

ControlDesigner has a virtual property SnapLines, but most designers override the property, in other words, most designers have customized SnapLines

Code flow before PR10279

when BehaviorService or DragAssistanceManager accesses SnapLines , customized SnapLines were returned.

Code flow after PR10279

ControlDesigner.cs

when BehaviorService or DragAssistanceManager accesses SnapLinesInternal , customized SnapLines were skipped.

Proposed changes

• Use SnapLines

Screenshots

Before

After

Test methodology

• manually

[codecov]

Codecov Report

Attention: Patch coverage is 97.72727% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.86194%. Comparing base (61ec31a) to head (4e0694c).
Report is 16 commits behind head on release/9.0.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/9.0      #13349         +/-   ##
=====================================================
+ Coverage     74.83837%   74.86194%   +0.02357%     
=====================================================
  Files             3022        3022                 
  Lines           630464      630506         +42     
  Branches         46801       46801                 
=====================================================
+ Hits            471829      472009        +180     
+ Misses          155246      155114        -132     
+ Partials          3389        3383          -6     

Flag	Coverage Δ
Debug	74.86194% <97.72727%> (+0.02357%)	⬆️
integration	18.02409% <50.00000%> (+0.01304%)	⬆️
production	47.91853% <50.00000%> (+0.04851%)	⬆️
test	97.00042% <100.00000%> (+0.00037%)	⬆️
unit	44.95149% <0.00000%> (+0.06962%)	⬆️

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