change: pass Scope into Resource::read() and Resource::with()

[gbj]

Calling Resource::read() or Resource::with() crawls up the Scope tree, looking for the nearest <Suspense/> component, if any. This is used for streaming resource and suspense data from the server to the client during initial load, which is a significant optimization over waiting to start loading data until Wasm has loaded on the client.

Previously, a Scope was given to the Resource when it was created, and it carried this Scope around with it. Unfortunately, this meant that a Resource created in a "higher" scope couldn't be read correctly under a "lower" <Suspense/>. For example, if you created a resource in the root of your application, reading it under a <Suspense/> in one of your routes would not correctly register with the suspense, so would not properly stream.

This PR corrects that behavior for the hopefully-small cost of passing the omnipresent cx as the first argument to Resource::read() and Resource::with(). Now, you can create a single Resource somewhere in your app, pass it to multiple parts of the app via provide_context, and read it under multiple streaming <Suspense/> components while only actually loading the resource once.