Replace QuicString with std::string, pass 1

This replaces QuicString with std::string in all of the "QUIC proper".  I will
delete QuicString once all code using it is gone.

gfe-relnote: n/a (no functional change)
PiperOrigin-RevId: 237872023
Change-Id: I82de62c9855516b15039734d05155917e68ff4ee
diff --git a/quic/test_tools/simulator/alarm_factory.h b/quic/test_tools/simulator/alarm_factory.h
index 535095a..d765175 100644
--- a/quic/test_tools/simulator/alarm_factory.h
+++ b/quic/test_tools/simulator/alarm_factory.h
@@ -14,7 +14,7 @@
 // AlarmFactory allows to schedule QuicAlarms using the simulation event queue.
 class AlarmFactory : public QuicAlarmFactory {
  public:
-  AlarmFactory(Simulator* simulator, QuicString name);
+  AlarmFactory(Simulator* simulator, std::string name);
   AlarmFactory(const AlarmFactory&) = delete;
   AlarmFactory& operator=(const AlarmFactory&) = delete;
   ~AlarmFactory() override;
@@ -26,10 +26,10 @@
 
  private:
   // Automatically generate a name for a new alarm.
-  QuicString GetNewAlarmName();
+  std::string GetNewAlarmName();
 
   Simulator* simulator_;
-  QuicString name_;
+  std::string name_;
   int counter_;
 };