* feat: add will-redirect to allow people to prevent 30X redirects
* spec: add tests for the will-redirect event
* refactor: implement will-redirect using NavigationThrottle instead of PostTask
This avoids a potential race condition and immediately cancels the
navigation
* docs: add docs for did-redirect-navigation
* refactor: move AtomNavigationThrottle out of net folder
* refactor: update header guard for atom_navigation_throttle.h
* refactor: fix chromium style errors in the GN build
* refactor: update throttle impl to NOTREACHED and std::make_unqique
