Notify quicconnectionvisitorinterface when forward progress is made after path degrading. No flag protection, no-op in the shared code. Chromium QuicChromiumClientSession will override OnForwardProgressMadeAfterPathDegrading to handle differently. PiperOrigin-RevId: 315999536 Change-Id: Ibc7ac1ca4c8a38cba29b67f5bd366b29d9d85df3