[Cocoa] Remote video codecs should surface any error happening during encoding to web pages
<rdar://problem/118770776>
Pull request: https://github.com/WebKit/WebKit/pull/20876
Committed 271377@main (279e75f6851c): <https://commits.webkit.org/271377@main> Reviewed commits have been landed. Closing PR #20876 and removing active labels.