Add enough BNF support for all CSS property longhand grammars
<rdar://problem/103795673>
Pull request: https://github.com/WebKit/WebKit/pull/8115
Committed 258381@main (0e7b8c42e6a0): <https://commits.webkit.org/258381@main> Reviewed commits have been landed. Closing PR #8115 and removing active labels.