Implement with and round methods for TemporalPlainDate[Time]
Pull request: https://github.com/WebKit/WebKit/pull/4420
Committed 254565@main (2f0cbc36b534): <https://commits.webkit.org/254565@main> Reviewed commits have been landed. Closing PR #4420 and removing active labels.
<rdar://problem/100036978>