[go_router_builder] Add routing functions to GoRouteData

[StevenSorial]

fixes #106790

This PR adds the routing methods .location, .go(context), .push(context), .pushReplacement(context), and replace(context) to GoRouteData and changes the generation to use a mixin instead of an extension. I believe this increases flexibility by allowing the base class to be passed around the app.

Feel free to suggest modifying the versioning.

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