Provides access to the navigator stack

[jihongboo]

Our app needs to report some even trapping, which have information related to the navigator stack, such as the current page and the previous page.
Currently, we get the navigator stack information by getting the NavigationPath and then parsing it, but the sheet and cover information cannot be obtained from the NavigationPath.
It would be very helpful if Navigator could log and access the navigator stack information in the framework.

[hmlongco]

Probably not going to happen for two reasons.

First is that NavigationPath is opaque.

Second is that once NavigationPath is exposed I'll have to leave it that way, even if Apple improves the mechanisms in the future.

Destinations, checkpoints, send... all exist in order to leave views in the dark about where they are, how they got there, and how to return.

I've been considering adding a few new logging conditions, but navigation is problematic when used initiated swipe gestures are used to pop and dismiss views.