Allow QuicSentPacketManager to expose the setter of num_ptos_for_path_degrading_.
Allow QuicSentPacketManager to expose the setter of num_ptos_for_path_degrading_.

This will allow Envoy to config the number of ptos it wants for path degrading alarm.

PiperOrigin-RevId: 405425564

google/quiche,google/quiche,google/quiche,google/quiche