[typescript-fetch] runtime: pass init and url as returned by the premiddleware to the postmiddleware

Created by: FabianSellmann

Current implementation will always pass the initial url and init object. However if a pre middleware returns an object whose init or url property refer to a different url string or object, any following post middleware wont have access to it. Effectively providing the post middleware with completely different request information then what was actually used to make the fetch call.

The change here is very minimal to use the init and url from the fetchParams as potentially returned by the pre middleware.

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