Hot Restart for ASP.NET Core during inner-loop

Keep process alive between application "restarts" in the inner-loop.

Some considerations:
- Keeping client connections alive/queued while app restarts so browser doesn't show an error
- Implementing at the native host level (Kestrel/IIS Express)
- Implementing at the managed host level (startup hooks, `AssemblyLoadContext`)
- Implementing at the `Host` API level (generic host)
- Avoiding reprocessing of server bindings between restarts
- Avoiding reconstruction of the IoC container between restarts
- Avoiding rebuilding the route table between restarts
- Which component is letting us know the app needs to be restarted? (`dotnet watch`, IDE, etc.)
- How do we get the new assemblies for the app that needs to be restarted? Read from disk in usual location assuming a standard build (or some other compilation) has taken place? Receive assemblies as bytes via IPC?