gfe-relnote: Add support for 1RTT and 2RTT connection options in BBRv2, which reduce the number of rounds in STARTUP without a 25% bandwidth increase to 1 and 2 round trips, respectively.  Protected by gfe2_reloadable_flag_quic_bbr2_fewer_startup_round_trips.
gfe-relnote: Add support for 1RTT and 2RTT connection options in BBRv2, which reduce the number of rounds in STARTUP without a 25% bandwidth increase to 1 and 2 round trips, respectively.  Protected by gfe2_reloadable_flag_quic_bbr2_fewer_startup_round_trips.

PiperOrigin-RevId: 306924645
Change-Id: I3fb267f0abe90811772ddc78130aaa7a18c3e705

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