Fix DockPanel measuring bug

[Poker-sang]

Fixes

Fix DockPanel measuring bug

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

When set H/V Spacing and H/V Alignment is not Stretch, the last child on this orientation would be clipped. (The length of the clips is the length of the spacing.)

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• [x] Based off latest main branch of toolkit
• [x] Tested code with current supported SDKs
• [ ] New component
  • [ ] Documentation has been added
  • [ ] Sample in sample app has been added
  • [ ] Analyzers are passing for documentation and samples
  • [ ] Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• [ ] Tests for the changes have been added (if applicable)
• [ ] Header has been added to all new source files
• [x] Contains NO breaking changes

Other information