fix(TextBox): fix MaxLength to work correctly with paste (backport #19665)

[mergify]

GitHub Issue (If applicable): closes #19591

PR Type

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

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.
• Commits must be following the Conventional Commits specification.

Other information

Internal Issue (If applicable):

---

This is an automatic backport of pull request #19665 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of c823cfa has failed:

On branch mergify/bp/release/stable/5.6/pr-19665
Your branch is up to date with 'origin/release/stable/5.6'.

You are currently cherry-picking commit c823cfa231.
  (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.UI/UI/Xaml/Controls/TextBox/TextBox.skia.cs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Uno.UI/UI/Xaml/Controls/TextBox/TextBox.cs

Cherry-pick of 1d80eed has failed:

On branch mergify/bp/release/stable/5.6/pr-19665
Your branch is ahead of 'origin/release/stable/5.6' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 1d80eed04e.
  (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)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/Given_TextBox.skia.cs

no changes added to commit (use "git add" and/or "git commit -a")

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

[unodevops]

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[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-20114/index.html

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[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-20114/index.html

[unodevops]

🤖 Your WebAssembly Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-20114/index.html

[unodevops]

⚠️⚠️ The build 163460 has failed on Uno.UI - CI.

[github-actions]

This PR is stale because it has been open 60 days with no activity. Remove stale label or comment or it will be closed in 10 days.

[jeromelaban]

Let's skip for now, moving to uno 6 fixes the issue.