This was never used, so let's get rid of it.

This defaults `ip_range_blacklist` to reserved IP ranges and also adds an
`ip_range_whitelist` setting to override it.

remove the stubbing out of `request.process`, so that `requestReceived` also renders the request via the appropriate resource.

Replace render() with a stub for now.

Where we want to render a request against a specific Resource, call the global
make_request() function rather than the one in HomeserverTestCase, allowing us
to pass in an appropriate `Site`.

Fixes #6755