fix(Catalyst): File and folder Picker UIThread issue

[ajpinedam]

GitHub Issue (If applicable): closes #15504

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

Getting: UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread when using FolderPicker and FileOpenPicker.

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.
• [x] Contains NO breaking changes
• [x] Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• [x] Commits must be following the Conventional Commits specification.

Other information

Internal Issue (If applicable):

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-15546/index.html

[unodevops]

🤖 Your WebAssembly Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-15546/index.html

[jeromelaban]

@mergifyio backport release/stable/5.1

[mergify[bot]]

backport release/stable/5.1

✅ Backports have been created

• #15554 fix(Catalyst): File and folder Picker UIThread issue (backport #15546) has been created for branch release/stable/5.1