Change BlockingConcurrentDequeue to provide IsEmpty property

Author: rjmholt

src/PowerShellEditorServices/Services/PowerShell/Execution/BlockingConcurrentDeque.cs

@@ -39,7 +39,7 @@ public BlockingConcurrentDeque()
             };
         }
 
-        public int Count => _queues[0].Count + _queues[1].Count;
+        public bool IsEmpty => _queues[0].Count == 0 && _queues[1].Count == 0;
 
         public void Prepend(T item)
         {

src/PowerShellEditorServices/Services/PowerShell/Host/PsesInternalHost.cs

@@ -691,7 +691,7 @@ private void OnPowerShellIdle()
                 }
             }
 
-            if (!runPipelineForEventProcessing && _taskQueue.Count == 0)
+            if (!runPipelineForEventProcessing && _taskQueue.IsEmpty)
             {
                 return;
             }