Add flag to QuicSession indicating that it has been configured

This CL adds a flag to QuicSession that indicates when the QuicSession has been
configured. This needed for follow-on work where IETF QUIC is limited as to the
frames that can be sent _until_ the transport config has been performed.

QuicSession test has been modified to A) artificially perform a configuration
and B) check at test termination that it has been configured.

gfe-relnote: N/A not significant. Other changes all to tests.
PiperOrigin-RevId: 264362154
Change-Id: I1467cd4ed4531c01950d3fb938637e8633de815e
diff --git a/quic/core/quic_session.cc b/quic/core/quic_session.cc
index 5486e64..fd3d489 100644
--- a/quic/core/quic_session.cc
+++ b/quic/core/quic_session.cc
@@ -89,7 +89,8 @@
       last_message_id_(0),
       closed_streams_clean_up_alarm_(nullptr),
       supported_versions_(supported_versions),
-      use_http2_priority_write_scheduler_(false) {
+      use_http2_priority_write_scheduler_(false),
+      is_configured_(false) {
   closed_streams_clean_up_alarm_ =
       QuicWrapUnique<QuicAlarm>(connection_->alarm_factory()->CreateAlarm(
           new ClosedStreamsCleanUpDelegate(this)));
@@ -1051,6 +1052,7 @@
     OnNewSessionFlowControlWindow(
         config_.ReceivedInitialSessionFlowControlWindowBytes());
   }
+  is_configured_ = true;
 }
 
 void QuicSession::AdjustInitialFlowControlWindows(size_t stream_window) {