MLECO-3164: Additional refactoring of KWS API

Part 1
* Add KwsClassifier
* KwsPostProcess can now be told to average results
* Averaging is handlded by KwsClassifier
* Current sliding window index is now an argument of DoPreProcess

Change-Id: I07626da595ad1cbd982e8366f0d1bb56d1040459
diff --git a/tests/use_case/kws/KWSHandlerTest.cc b/tests/use_case/kws/KWSHandlerTest.cc
index db67e54..413e089 100644
--- a/tests/use_case/kws/KWSHandlerTest.cc
+++ b/tests/use_case/kws/KWSHandlerTest.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021 Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2022 Arm Limited. All rights reserved.
  * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -23,6 +23,7 @@
 #include "UseCaseHandler.hpp"
 #include "Classifier.hpp"
 #include "UseCaseCommonUtils.hpp"
+#include "BufAttributes.hpp"
 
 namespace arm {
     namespace app {