Support logging ssl_handshake_processing_time for QUIC as well.

The purpose of this is to measure time taken by the GFE for the SSL handshake, not including time waiting for the client. I.e., it's just the aggregate time in the GFE process for the handshake.

I wasn't sure what the the best approach is, so please let me know if tracking this time in a different place would be better.

PiperOrigin-RevId: 379360130
diff --git a/quic/core/tls_handshaker.h b/quic/core/tls_handshaker.h
index dba8ea5..3bfdac6 100644
--- a/quic/core/tls_handshaker.h
+++ b/quic/core/tls_handshaker.h
@@ -57,7 +57,7 @@
  protected:
   // Called when a new message is received on the crypto stream and is available
   // for the TLS stack to read.
-  void AdvanceHandshake();
+  virtual void AdvanceHandshake();
 
   void CloseConnection(QuicErrorCode error, const std::string& reason_phrase);
   // Closes the connection, specifying the wire error code |ietf_error|