Improve ChromeTraceUtil logging, allow filename to be specified.

Expose this ChromeTraceUtil  logging to C-API: start/statelogging and submitProfileTiming
pybullet.submitProfileTiming, and STATE_LOGGING_PROFILE_TIMINGS used in startStateLogging
added example for Python profileTiming.py and C++ b3RobotSimulatorClientAPI::submitProfileTiming

src/Bullet3Common/b3HashMap.h

@@ -399,6 +399,18 @@ protected:
 		return &m_valueArray[index];
 	}
 
+	 Key getKeyAtIndex(int index)
+    {
+        b3Assert(index < m_keyArray.size());
+        return m_keyArray[index];
+    }
+    
+    const Key getKeyAtIndex(int index) const
+    {
+        b3Assert(index < m_keyArray.size());
+        return m_keyArray[index];
+    }
+
 	Value* operator[](const Key& key) {
 		return find(key);
 	}