fix infinite loops and remove public apis (#5954)

fix infinite loops and remove public apis (#5954)

* fix infinite loops and remove public apis

* - remove comments, fix location to not have implicit

* force uri to be relative on ios when no scheme specified

* address PR comments

* add error message

* reformat absolute uris

* additional suggestions

* Update Xamarin.Forms.Core/Shell/ShellNavigationState.cs

Co-Authored-By: PureWeen <shane94@hotmail.com>
* Update Xamarin.Forms.Core/Shell/ShellUriHandler.cs

Co-Authored-By: PureWeen <shane94@hotmail.com>
* Update Xamarin.Forms.Core/Shell/ShellUriHandler.cs

Co-Authored-By: PureWeen <shane94@hotmail.com>
* Update Xamarin.Forms.Core/Shell/ShellUriHandler.cs

Co-Authored-By: PureWeen <shane94@hotmail.com>