Unreviewed, fix build of CompactPointerTuple. This class needs std::exchange but doesn't #include <utility>.
Pull request: https://github.com/WebKit/WebKit/pull/4063
Committed 254197@main (4f2adf003382): <https://commits.webkit.org/254197@main> Reviewed commits have been landed. Closing PR #4063 and removing active labels.