When getting cookies only expose their name and value

[annevk]

As suggested in WebKit/standards-positions#36 (comment) which builds upon feedback from Ehsan https://wicg.github.io/cookie-store/#dictdef-cookielistitem should only have name and value members. This would keep parity with document.cookie in terms of what cookie aspects end up being exposed.

This is also what we plan to implement in WebKit.

[annevk]

cc @szewai @RupinMittal @bakulf

[bakulf]

Firefox is experimenting with the CookieStore API, and we have implemented what @annevk suggests here. get and getAll return only names and values.