[fetch] Integrate "subresource" integrity (#85)

Now it's implemented all over, it's probably time to remove the Fetch monkey patching from SRI and make it a proper part of Fetch.

https://github.com/w3c/webappsec/issues/428 has a question for @fmarier and co that needs to be answered first. I suspect the answer is yes.

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/85