net: Use RequestId to cancel fetches instead of creating an IPC channel (#34883)

Instead of creating an IPC channel for every fetch, allow cancelling
fetches based on the `RequestId` of the original request. This requires
that `RequestId`s be UUIDs so that they are unique between processes
that might communicating with the resource process.

In addition, the resource process loop now keeps a `HashMap` or `Weak`
handles to cancellers and cleans them up.

This allows for creating mutiple `FetchCanceller`s in `script` for a
single fetch request, allowing integration of the media and video
elements to integrate with the `Document` canceller list -- meaning
these fetches also get cancelled when the `Document` unloads.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/script_module.rs

@@ -1780,7 +1780,7 @@ fn fetch_single_module_script(
                 network_listener.into_callback(),
             );
         },
-        None => global.fetch_with_network_listener(request, network_listener, None),
+        None => global.fetch_with_network_listener(request, network_listener),
     }
 }