[Simple text codepath] Shadow TextRun's direction within WidthIterator so we can make local changes to it
<rdar://problem/114857993>
Pull request: https://github.com/WebKit/WebKit/pull/17371
Committed 267582@main (0c0e78b43702): <https://commits.webkit.org/267582@main> Reviewed commits have been landed. Closing PR #17371 and removing active labels.