experimental: Add scroll state to beforeNavigate and afterNavigate

[elliott-with-the-longest-name-on-github]

Would close #9914

This seems to work in all of the circumstances I could figure out. Here's a test app to play around with: https://github.com/tcc-sejohnson/test-sk-nav-scrollstate

Just make sure the pnpm overrides are pointing at a local version of kit checked out to this branch.

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[elliott-with-the-longest-name-on-github]

Closing in favor of a new implementation I whipped up, will open a new PR