Get Named Cookie seems broken for multiple cookies with the same name

[johannhof]

Get Named Cookie seems oblivious to the fact that there can be multiple cookies with the same name in the same context, e.g. through having a different Path. The spec (which seems broken in various ways) seems to assume that there is only one cookie with a given name.

We could refer to the sorting (step 2) in the Cookies RFC (though that mentions it might not be reliable), but it's probably preferable to simply integrate with the new Cookie Layering spec instead.

Ideally, we should offer a way to get all Cookies of the same name.

cc @annevk @DCtheTall

[annevk]

What happens in implementations today?

cc @burg @sysrqb