Two-way communication for QWebSockets created in QHttpServer does not work

QWebSockets created from the TCP socket listened to by QHttpServer only allow communication from server to client. This bug is likely to be introduced by the refactoring of QWebSocket verification in QHttpServer during the development of Qt 6.8.

Also add tests that two-way communication works after a QWebSocket is created on the QHttpServer. Because the current auto tests only check that QWebSocket connections are created successfully.