Add ALPN to QUIC when using TLS

This CL makes our client send ALPN when using QUIC with TLS, makes the server echo the first ALPN value, and allows quic_client to override the ALPN for IETF interop events.

gfe-relnote: protected by disabled flag quic_supports_tls_handshake
PiperOrigin-RevId: 242682444
Change-Id: I7e60fb61c0afe02283e38598de29df9018b71ee8
diff --git a/quic/core/tls_handshaker.cc b/quic/core/tls_handshaker.cc
index 17e2674..c6394b8 100644
--- a/quic/core/tls_handshaker.cc
+++ b/quic/core/tls_handshaker.cc
@@ -236,6 +236,8 @@
   // (draft-ietf-quic-transport-14, section 11.3). However, according to
   // quic_error_codes.h, this QUIC implementation only sends 1-byte error codes
   // right now.
+  QUIC_DLOG(INFO) << "TLS failing handshake due to alert "
+                  << static_cast<int>(desc);
   CloseConnection(QUIC_HANDSHAKE_FAILED, "TLS handshake failure");
 }