Forward error output from testhost as info (#5193)

Author: nohwnd

src/Microsoft.TestPlatform.TestHostProvider/Hosting/TestHostManagerCallbacks.cs

@@ -58,7 +58,9 @@ public void ErrorReceivedCallback(StringBuilder testHostProcessStdError, string?
  testHostProcessStdError.AppendSafeWithNewLine(data);
  if (_forwardOutput && _messageLogger != null && !StringUtils.IsNullOrWhiteSpace(data))
  {
- _messageLogger.SendMessage(TestMessageLevel.Error, data);
+ // Forward the error output, but DO NOT forward it as error. Until now it was only written into logs,
+ // and applications love to write Debug messages into error stream. Which we do not want to fail the test run.
+ _messageLogger.SendMessage(TestMessageLevel.Informational, data);
  }
  }