Add TAO destination check for navigation redirect chains

[yoavweiss]

As part of the WebPerfWG discussion on re-exposing redirectCount for opted-in cross-origin redirects, we discussed the fact that TAO currently only opts-in "backwards" in terms of origins, and doesn't constitute an opt-in to the destination origin, which is the appropriate opt-in for navigations (contrary to subresources).

This PR adds the mechanisms that can enable such "forward" opt-in, and can enable a response to a redirect chain to know that the redirect chain opted in to expose the redirects to its origin.

Once this lands, we'd use the relevant algorithms in the related HTML PR.

• At least two implementers are interested (and none opposed):
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• Tests are written and can be reviewed and commented upon at:
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• Implementation bugs are filed:
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• MDN issue is filed: …
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