[Enhancement] GetNavigationUriPath For Maui

Summary

In Prism Forms we had the extension method GetNavigationUriPath, which when called would give you the current Uri of the INavigationService. In maui this extension no longer exists and reading the current Uri from a Viewmodel is incredibly difficult. We can observe the current Uri using the global navigation observer, however performing viewmodel based logic on the current Uri path is difficult.

API Changes

Add a new INavigationServiceExtension method named GetNavigationUriPath

Intended Use Case

Performing logic in a view model based on the page uri stack. For example we could have a Login page which can be accessed in multiple ways:

1. Open app for the first time, see a welcome flow & agree to privacy policy, complete flow and show login page. For this scneario we want to show a back button to go back into the privacy flow
2. Open app after agreeing to privacy, go directly to the login page. In this case we don't want to show a back button because we are at the bottom of our navigation stack.

Start by locating the MAUI navigation service and the INavigationServiceExtension methods, then compare them with Prism Forms' existing GetNavigationUriPath behavior. Implement the requested API so view models can read the current navigation URI path, and verify that it supports both navigation scenarios described in the issue.