Add CRNT to Cronet QUIC connection options.

This will allow us to distinguish Cronet traffic in the query logs

PiperOrigin-RevId: 672478483

quiche/quic/core/crypto/crypto_protocol.h

diff --git a/quiche/quic/core/crypto/crypto_protocol.h b/quiche/quic/core/crypto/crypto_protocol.h
index bca410b..e55af80 100644
--- a/quiche/quic/core/crypto/crypto_protocol.h
+++ b/quiche/quic/core/crypto/crypto_protocol.h
@@ -286,6 +286,8 @@
                                                  // packets to both addresses.
 const QuicTag kEVMB = TAG('E', 'V', 'M', 'B');
 
+const QuicTag kCRNT = TAG('C', 'R', 'N', 'T');
+
 // Optional support of truncated Connection IDs.  If sent by a peer, the value
 // is the minimum number of bytes allowed for the connection ID sent to the
 // peer.