chore: Fixing reference to UIWindow (backport #2246)

[mergify]

GitHub Issue (If applicable): closes #2240

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

UIWindow not found using the old _window field.

What is the new behavior?

v5.2 of Uno adds multi-window support along with refactoring inner logic for Window management.
the internal NativeWindow property now returns the UIWindow required for Maui Embedding

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• 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)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Updated the Release Notes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):

---

This is an automatic backport of pull request #2246 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 72b698f has failed:

On branch mergify/bp/release/stable/4.1/pr-2246
Your branch is ahead of 'origin/release/stable/4.1' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 72b698f29.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/Uno.Extensions.Maui.UI/MauiEmbedding.apple.cs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Directory.Packages.props

Cherry-pick of c193535 has failed:

On branch mergify/bp/release/stable/4.1/pr-2246
Your branch is ahead of 'origin/release/stable/4.1' by 4 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit c19353546.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   samples/MauiEmbedding/Directory.Build.props
	modified:   samples/MauiEmbedding/Directory.Packages.props
	modified:   samples/MauiEmbedding/MauiEmbedding.MauiControls/MauiEmbedding.MauiControls.csproj
	modified:   samples/MauiEmbedding/MauiEmbedding.Mobile/MauiEmbedding.Mobile.csproj
	modified:   src/Uno.Extensions.Hosting.UI/ApplicationBuilder.cs
	modified:   src/Uno.Extensions.Navigation.UI/Navigators/ContentDialogNavigator.cs
	modified:   src/Uno.Extensions.Navigation.UI/ServiceProviderExtensions.cs
	new file:   src/maui-embedding.props

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Directory.Packages.props

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally