Add a GFE QUIC varz to count the number of successful TLS handshakes by trait.

Also fixed a typo in tls_server_handshaker.cc, introduced in cl/363019712.

PiperOrigin-RevId: 363048399
Change-Id: I0c3b3c64290db50d45c46ad97704849011510575
diff --git a/quic/core/tls_server_handshaker.cc b/quic/core/tls_server_handshaker.cc
index b6a7d80..d21be71 100644
--- a/quic/core/tls_server_handshaker.cc
+++ b/quic/core/tls_server_handshaker.cc
@@ -757,7 +757,7 @@
                          decrypt_ticket_stats.async_latency,
                          "Async decrypt ticket latency in microseconds");
   }
-  connection_stats().tls_server_compute_signature_stats =
+  connection_stats().tls_server_decrypt_ticket_stats =
       std::move(decrypt_ticket_stats);
 
   return result;