Add generic GoBack and remove legacy GoBackTo

[berhir]

Description of Change

With #2818 the behavior of GoBack was extended to support navigating back to a specific viewName in the stack.
But there is currently no generic version of GoBack in the NavigationBuilder.

This PR adds the generic GoBack<TViewModel>() to the NavigationBuilder.

As suggested by dansiegel I have removed the legacy GoBackTo<TViewModel>() instead of marking it as obsolete.

The old GoBackTo worked differently and popped each page and called CanNavigateAsync, OnNavigatedFrom, and OnNavigatedTo of each page. Maybe there are cases when this is the desired behavior. So if you want to keep the old behavior, I suggest giving this methods a clear name to easily distinguish GoBack and GoBackTo. Just let me know and I can update the PR.

Bugs Fixed

None

API Changes

List all API changes here (or just put None), example:

Added:

• Task INavigationBuilder.GoBackAsync();

Removed:

• Task PageNavigationService.GoBackToAsync(string name, INavigationParameters parameters) calls GoBackAsync(name, parameters)
• Task INavigationServiceExtensions.GoBackToAsync(this INavigationService navigationService, string name)
• Task INavigationBuilder.GoBackTo(INavigationParameters parameters);
• Task NavigationBuilderExtensions.GoBackTo(this INavigationBuilder builder)

Behavioral Changes

GoBackTo was removed and GoBack works without calling CanNavigateAsync, OnNavigatedFrom, and OnNavigatedTo of each page.

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of master at time of PR
• Changes adhere to coding standard

[dansiegel]

Thanks for the PR