[Feature Request] PageStack: push and remove the specific stack pages in the background

[capdiem]

Assuming the stack of pages is page1 -> page2 -> page3 -> page4 -> page5, after invoking the following method

PageStackNavController.Push("/new-page", countOfStackPagesToDelete: 2);

the new stack should be page1 -> page2 -> page3 -> new-page.

If invoke the following method

PageStackNavController.Push("/new-page", deleteUtil: "/page3");

the new stack should be page1 -> page2 -> page3 -> new-page.