Migrate to ALLOW_***_BEGIN/END instead of #pragma clang diagnostic
<rdar://problem/108011779>
Pull request: https://github.com/WebKit/WebKit/pull/12711
Committed 262993@main (f204f5437c4e): <https://commits.webkit.org/262993@main> Reviewed commits have been landed. Closing PR #12711 and removing active labels.