Refactor Color IPC types to not be nested. Needed to help along the serializer generator in upcoming work.
<rdar://problem/117499465>
Pull request: https://github.com/WebKit/WebKit/pull/19569
Committed 269793@main (8a46e65b9cb7): <https://commits.webkit.org/269793@main> Reviewed commits have been landed. Closing PR #19569 and removing active labels.