Write the entire packet in SendData() synchronously.

This doesn't seem to regress performance and feels safer since we're now reusing the underlying byte array.

We're also saving on not allocating the Overlapped and NativeOverlapped data structures and various other async overhead.

src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs

@@ -766,13 +766,7 @@ public void SendData(INodePacket packet)
                         int lengthToWrite = Math.Min(writeStreamLength - i, MaxPacketWriteSize);
                         if (writeStreamLength - i <= MaxPacketWriteSize)
                         {
-                            // We are done, write the last bit asynchronously.  This is actually the general case for
-                            // most packets in the build, and the asynchronous behavior here is desirable.
-#if FEATURE_APM
-                            _serverToClientStream.BeginWrite(writeStreamBuffer, i, lengthToWrite, PacketWriteComplete, null);
-#else
                             _serverToClientStream.Write(writeStreamBuffer, i, lengthToWrite);
-#endif
                             return;
                         }
                         else
@@ -781,12 +775,7 @@ public void SendData(INodePacket packet)
                             // return out of this function and let the rest of the system continue because another operation
                             // might want to send data immediately afterward, and that could result in overlapping writes
                             // to the pipe on different threads.
-#if FEATURE_APM
-                            IAsyncResult result = _serverToClientStream.BeginWrite(writeStreamBuffer, i, lengthToWrite, null, null);
-                            _serverToClientStream.EndWrite(result);
-#else
                             _serverToClientStream.Write(writeStreamBuffer, i, lengthToWrite);
-#endif
                         }
                     }
                 }
@@ -814,23 +803,6 @@ public void Close()
                 _terminateDelegate(_nodeId);
             }
 
-#if FEATURE_APM
-            /// <summary>
-            /// Completes the asynchronous packet write to the node.
-            /// </summary>
-            private void PacketWriteComplete(IAsyncResult result)
-            {
-                try
-                {
-                    _serverToClientStream.EndWrite(result);
-                }
-                catch (IOException)
-                {
-                    // Do nothing here because any exception will be caught by the async read handler
-                }
-            }
-#endif
-
             private bool ProcessHeaderBytesRead(int bytesRead)
             {
                 if (bytesRead != _headerByte.Length)