Get All Cookies and Get Named Cookie need to consider Partitioned Cookies

It's currently not really possible to use Get All Cookies and Get Named Cookie with Partitioned Cookies (I haven't tested Delete All Cookies but we should probably do that).

It looks like we have undefined behavior, e.g. in the following scenario:

    document.cookie = "test0=a; Secure; Partitioned;";
    const cookies = await test_driver.get_all_cookies();
    const cookie = await test_driver.get_named_cookie("test0");

what are cookie and cookies in the above simple scenario? If you ask Chrome today, they're empty.

Because we did not have decent cookie spec infrastructure for a long time, the spec is a bit unclear on this, but I suspect that the intention is that any Cookie that is accessible to the current document (including HTTPOnly cookies) should be included in the return value, thus also partitioned cookies.

Note that this makes #1892 worse, because otherwise identical partitioned and unpartitioned cookies can both be accessible to the same context.

cc @annevk @bvandersloot-mozilla @dcthetall

Start with the Get All Cookies and Get Named Cookie entry points and the partitioned-cookie scenario in the issue. Determine the expected values for cookie and cookies, including whether accessible partitioned cookies are returned, and consider the related Delete All Cookies behavior. Done means the cookie commands have defined behavior for this case.