fix: Preventing recreation of pages when navigating back

[nickrandolph]

GitHub Issue (If applicable): https://github.com/unoplatform/uno.chefs/issues/105

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

When navigating back with a return value the previous page was being recreated, even if NavigationCacheMode set to Required (on Android)

[Also, on Xamarin Android an exception is raised when using Console logging]

What is the new behavior?

Removed code that was modifying the backstack - this is only used when retrieving the response value in the NavigatedTo event in the previous page - it's not used by Uno.Ext.Navigation, so removing this will not affect existing functionality.

[Also, removed console logging for Xamarin targets, and fixed build for the Legacy targets for testharness]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• [ N/A ] Docs have been added/updated which fit documentation template. (for bug fixes / features)
• [ N/A ] Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• [ N/A ] Updated the Release Notes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):