Adding parsing support for white-space-collapse longhand. https://drafts.csswg.org/css-text-4/#white-space-collapsing
<rdar://problem/109486162>
Pull request: https://github.com/WebKit/WebKit/pull/14265
Committed 264501@main (4cee6d1c66fa): <https://commits.webkit.org/264501@main> Reviewed commits have been landed. Closing PR #14265 and removing active labels.