BaselineContext holds multiple BaselineGroups and we should use that so the flex items are placed into the correct baseline sharing group. After that, we can perform the rest of the steps as described in the spec below https://drafts.csswg.org/css-align-3/#baseline-rules
<rdar://problem/109362699>
Pull request: https://github.com/WebKit/WebKit/pull/13968
Committed 266387@main (b7b43b9bf044): <https://commits.webkit.org/266387@main> Reviewed commits have been landed. Closing PR #13968 and removing active labels.