fix(XamlReader): Properly support TemplateBinding of attached properties

[Youssef1313]

GitHub Issue (If applicable): closes #13517

PR Type

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

Copilot Summary

🤖 Generated by Copilot at c187ba5

This pull request fixes a bug in the XamlReader that caused attached properties to be parsed incorrectly in some cases. It also updates the XamlObjectBuilder and the test assertions to follow the Xaml standard for attached properties and TemplateBindings.

PR Checklist

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• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
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Other information

Internal Issue (If applicable):

[Youssef1313]

CI keeps timing out even with restarts.

[Youssef1313]

/azp run

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