Use custom mobile testing API (#53871)

Use custom mobile testing API (#53871)

* Use custom Android testing API

* Fix for non-mobile cases

* Use Collection Fixtures for mobile only

* Update src/tests/Common/Coreclr.TestWrapper/MobileAppHandler.cs

Co-authored-by: Přemek Vysoký <premek.vysoky@microsoft.com>
* Update src/tests/Common/Coreclr.TestWrapper/MobileAppHandler.cs

Co-authored-by: Přemek Vysoký <premek.vysoky@microsoft.com>
* Update src/tests/run.proj

Co-authored-by: Přemek Vysoký <premek.vysoky@microsoft.com>
* Fix the ios app extension

* Add back Path and remove redundant namespace string

* Add missing class name Path

Co-authored-by: Přemek Vysoký <premek.vysoky@microsoft.com>