✨ Google Ad Manager Publisher first-party IDs

[glevitzky]

Addresses #40248.

Implements both cookie writing and reading components described in the linked I2I. In particular, we will set the specified cookies on the ad response HTTP header, and add those cookies to ad requests when available. We also add here some ads utility functions for verifying user consent for cookies, and some global cookie utility functions for checking whether setting cookies is allowed.

This change on its own is mostly a no-op, as serving is not yet setup to send to the new HTTP cookie header.

[erwinmombay]

@ychsieh could you help me review this while @powerivq is out

[erwinmombay]

@glevitzky do you know if the failing unit tests are related to this change?

1) should stay in modal if focus stays in modal and close if outside
     amp-lightbox component  
     AssertionError: expected close to have been called exactly once, but it was called 0 times
    at http://localhost:9876/home/circleci/project/extensions/amp-lightbox/0.1/test/test-amp-lightbox.js:250:29

2) uses custom CSS when element is focused
     amp-social-share  

[erwinmombay]

should probably be {!Event}

[erwinmombay]

non blocking, but can this value be memoized in some fashion?
would be happy with a comment/note if yes.

[glevitzky]

I'm sure it's a tiny edge case, but strictly speaking, a user can disable cookies on their browser at any time, invalidating our previously memoized value.

[glevitzky]

Test failures look unrelated. Running amp unit --verbose --files="extensions/amp-lightbox/0.1/test/test-amp-lightbox.js" from a clean branch results in the same failure.

[powerivq]

Do we want to do a design review for this?