Replace OverlayScrollbarSizeRelevancy and ShouldRespectOverflowClip with an OptionSet<>, because I will be adding a new argument.
Pull request: https://github.com/WebKit/WebKit/pull/2652
Committed 252758@main (b7e27bd9c786): <https://commits.webkit.org/252758@main> Reviewed commits have been landed. Closing PR #2652 and removing active labels.
<rdar://problem/97469834>