These helpers are often imported by various tests throughout the
repository, but the helpers aren't exported/exposed from the public
entry-point; even though they confusingly reside in there.
This commit fixes this, and moves the helpers into
`packages/private/testing`. This is a preparation for the `ts_project`
migration where we don't want to leverage deep imports between packages.
PR Close#61476
This commit adds the ability to directly abort a navigation through the
`Router.getCurrentNavigation()?.abort()` method. While there are no
feature requests for this, it is a feature that will be necessary for
integration with the navigation API. The API enables better tracking of
an ongoing navigation for SPAs and a site visitor can cancel a
navigation by clicking the stop button in the browser. While this could
technically be done on the transition with an internal jsdoc comment to
hide it from application developers, there's no need.
With this feature, I believe it would be possible to create somewhat of a shim
to integrate with the navigation API even before the router has full support
using the router events to control a deferred navigation that never
commits the URL and always aborts itself on navigation end.
PR Close#60380