QuartcFactory cleanup part 1: delete the QuartcFactory object.

QuartcFactory is really just a wrapper for a QuicConnectionHelperInterface and a
function to create a QuartcClientSession.  There's no need for the object.
Instead, CreateQuartcClientSession is now a free function.

gfe-relnote: n/a (Quartc only)
PiperOrigin-RevId: 239778175
Change-Id: I2f7481563f994fb8b364985222c91cbad923af89
diff --git a/quic/quartc/quartc_endpoint.h b/quic/quartc/quartc_endpoint.h
index c78641f..97f3060 100644
--- a/quic/quartc/quartc_endpoint.h
+++ b/quic/quartc/quartc_endpoint.h
@@ -108,11 +108,8 @@
   // calls the delegate.
   std::unique_ptr<QuicAlarm> create_session_alarm_;
 
-  // QuartcFactory used by this endpoint to create sessions.  This is an
-  // implementation detail of the QuartcEndpoint, and will eventually be
-  // replaced by a dispatcher (for servers) or version-negotiation agent (for
-  // clients).
-  std::unique_ptr<QuartcFactory> factory_;
+  // Helper used by QuicConnection.
+  std::unique_ptr<QuicConnectionHelperInterface> connection_helper_;
 
   // Config to be used for new sessions.
   QuartcSessionConfig config_;