Add the ability for the IPCTestingAPI to report when a sync message fails to be received correctly
<rdar://problem/118188347>
Pull request: https://github.com/WebKit/WebKit/pull/20249
Committed 270705@main (e36c14395c0e): <https://commits.webkit.org/270705@main> Reviewed commits have been landed. Closing PR #20249 and removing active labels.