[Enhancement] Remove IPlatformNavigation

[dansiegel]

Summary

Since we are no longer trying to share the INavigationService from Prism.Core and INavigationService is back in Prism.Forms we no longer have a hard requirement for IPlatformNavigationService. While this would be another pdb break from 7.X, the 8.0 push would be a good time to remove the API bloat and simply put this in the INavigationService

API Changes

• Removes IPlatformNavigationService
• Adds INavigationService.GoBackAsync(INavigationParameters, bool?, bool)
• Adds INavigationService.GoBackToRoot(INavigationParameters)
• Adds INavigationService.NavigateAsync(string, INavigationParameters, bool?, bool)
• Adds INavigationService.NavigateAsync(Uri, INavigationParameters, bool?, bool)

Intended Use Case

Removes issues with Mocking INavigationService where people use these API's where their NavigationService also needed to implement IPlatformNavigationService.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.