Remove react-router on the server, or upgrade to server context

[jplhomer]

Remove react-router on the server, and build our own simple routing engine powered by regex, OR upgrade it to server context (upstream)

[blittle]

For some reason, this PR introduces a weird context problem. Details:

1. The app loads fine with one browser
2. If two separate browsers load the app at the same time or if you load the app and then quickly refresh before the initial streaming completes, a context error occurs.
3. The context error shows up in the SSR streaming phase. Because of the error, the page goes white, but then the client eventually makes the hydration request. That succeeds and the page fully renders.
4. It happens outside of vite, when running a production node server.
5. Upgrading to the latest version of React 18 doesn't help

The context is phone, it's just for some reason it has the default context value (when it shouldn't). Somehow is global data like context getting bled between requests? Maybe the second request is reseting the context of the first?