Fix scroll restoration when server props are changed

[jplhomer]

Description

Fixes #1141

This adds an additional state to only fire the scroll restoration logic when a location has changed, not when pending has changed.

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[nattyg93]

Will this trigger the "scroll to top" behaviour when the pathname does not change, but search does? I ask, because in our app, we often use the search to keep track of filters (form inputs) on a page, and it would break the UX if it scrolled to the top whenever a user updates one of the filters. However, on a different page, we use the search for pagination - at which point we do want it to scroll to top. However, we are able to handle this later case in our code with a useEffect and window.scrollTo(0, 0). So my thinking is that for our particular usecase(s), we either need some sort of escape hatch to say: "please don't scroll the top when I change these only the search" OR don't scroll to the top when the only the search changes and we can handle manually scrolling to the top when our intended UX calls for it.

[jplhomer]

Will this trigger the "scroll to top" behaviour when the pathname does not change, but search does?

Correct. This is the behavior you get natively in the browser, and we would want to preserve that.

please don't scroll the top when I change these

Maybe something like Next.js shallow routing is the answer here? Where we'd allow some sort of prop like <Link scrollToTop={false}> which indicates that the URL should change and RSC is fetched, but the scroll position should not change?

[jplhomer]

Update: I realized that you can actually accomplish this without us needing a new API:

1. Manually call setServerProps and use an alternate path, like _search or _filter
2. Call window.history.pushState() in your client component to update the URL. This does not affect scroll position.
3. In your server component, look for both params (real search and alternate path). This allows you to present the correct filter values for both initial page loads and realtime RSC updates.