gfe-relnote: When new 0RTT key is available, only allow client to write application data as server application data should be written in forward secure. Protected by gfe2_reloadable_flag_quic_use_handshaker_delegate2 which replaces gfe2_reloadable_flag_quic_use_handshaker_delegate. PiperOrigin-RevId: 284213052 Change-Id: Ic77723e7f8570fb720af719af98d86e47c76ad34