Support IETF RETRY from client

This CL parses the retry token, and updates our connection ID and crypters. Server-side support will come in a subsequent CL which will also add end to end tests.

gfe-relnote: Support IETF Retry packets from client in v99, protected by disabled v99 flag
PiperOrigin-RevId: 246911895
Change-Id: Icd5ecd22190fd18ad42882a66c3aa470640ce223
diff --git a/quic/core/quic_packets.h b/quic/core/quic_packets.h
index e745e07..3ced31f 100644
--- a/quic/core/quic_packets.h
+++ b/quic/core/quic_packets.h
@@ -102,6 +102,7 @@
   // parsed from the packet buffer. IETF QUIC only, always false for GQUIC.
   bool has_possible_stateless_reset_token;
   QuicPacketNumberLength packet_number_length;
+  uint8_t type_byte;
   ParsedQuicVersion version;
   // nonce contains an optional, 32-byte nonce value. If not included in the
   // packet, |nonce| will be empty.