Implement set function in Cookie Store API
Pull request: https://github.com/WebKit/WebKit/pull/15824
<rdar://problem/112176104>
Committed 266064@main (7d9eadacc380): <https://commits.webkit.org/266064@main> Reviewed commits have been landed. Closing PR #15824 and removing active labels.
<rdar://problem/112687049>