Update the WebView docs to point to MDN for cookie attribute explanations with...

Update the WebView docs to point to MDN for cookie attribute explanations with an explicit callout for the Partitioned attribute.

Cherry picked I35d175ee34f1838f4db11c41a4115950fdb8b3f8 to master due to b/286408867.

Code was merged via `-s ours` and is missing even though the sha exists on the target branch. Cherry pick is required to bring in the code.

Manually remove the "Merged in" directive to allow for downstream propagation.

(cherry picked from https://android-review.googlesource.com/q/commit:09c55022b7623b6ed94123eed8da9006087d4107)
Change-Id: Iec51cfd48db0b2662b2c57d380417124e962ec57