refactor!: TemplatedParent rework

[Xiaoy312]

GitHub Issue (If applicable): closes #1621, closes #12624

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

todo

What is the new behavior?

todo

Copilot Summary

🤖 Generated by Copilot at 4f37e52

This pull request adds support for template bindings, which allow bindings to use the templated parent as the source. It modifies the BindingExpression, Binding, ControlTemplate, DataTemplate, ItemsPanelTemplate, and Control classes to handle the templated parent scope and pass it to the bindings. It also adds a new class TemplateParentResolver to create and manage the templated parent scopes.

PR Checklist

Please check if your PR fulfills the following requirements:

• 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

[Xiaoy312]

to be reworked completely...
we should be modifying the generated xaml and the xaml parsing side
instead of correcting {TemplateBinding} between ControlTemplate materialization

[Xiaoy312]

after reviewing the approach, it was made clear that it is easier to maintain the global stack and inject the parent on BindingExpression.ctor
than to adjust the whole call chain (which touches source-gen + xamlreader and some of the unified parts)
plus even then, the other approach would still requires a global stack for the info (as that would be the only way, that I know of)
so the parent being injected earlier or later made near no difference at all.

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todo:

• templated parent rework
  • XamlCodeGenerator
  • XamlReader.Load
• write test cases against common scenarios
• adjust code around template recycling
• validate native control presenter tp propagation
• polish & clean up debug code
• rebase & sanity check