[go_router] Add navigator key to typed routes

[GP4cK]

This PR is the first step described in https://github.com/flutter/packages/pull/3439#discussion_r1136458688.

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[flutter-dashboard[bot]]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[GP4cK]

@chunhtai

1. Should I create a new issue just to say that we need these navigator keys?
2. For the tests, it seems trivial to add a test just to make sure we can create an instance of TypedShellRoute and TypedGoRoute by passing a navigator key. Shall I still do it?

[chunhtai]

This class is for annotation in go_router_builder, so I don't think it is testable in go_router package. The real test will be in go_router_builder when it starts to leverage the newly added parameters

[Hixie]

test-exempt: code will be tested when applicable logic is added

[auto-submit[bot]]

auto label is removed for flutter/packages, pr: 3471, due to - This commit is not mergeable and has conflicts. Please rebase your PR and fix all the conflicts.