HTTP/3: adjusted QUIC connection finalization. When an HTTP/3 function returns an error in context of a QUIC stream, it's this function's responsibility now to finalize the entire QUIC connection with the right code, if required. Previously, QUIC connection finalization could be done both outside and inside such functions. The new rule follows a similar rule for logging, leads to cleaner code, and allows to provide more details about the error. While here, a few error cases are no longer treated as fatal and QUIC connection is no longer finalized in these cases. A few other cases now lead to stream reset instead of connection finalization.