[IE TESTS] Move SLT classes to SharedTestClasses lib & add serialization functionality to the common class (#3431)

* [IE TESTS] Changing functional test utils structure

* Example

* Remove extra

* Apply comments

* fixes

* [IE TESTS] Change the structure

* Continue

* step 3

* [IE TESTS] Complete transition single layer test classes

* [IE TESTS] Transition Subgraph

* Fix subgraph namespaces

* fix

* Apply comments

* latm fix

docs/template_plugin/tests/functional/core_config.cpp

@@ -0,0 +1,8 @@
+// Copyright (C) 2020 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#include "functional_test_utils/core_config.hpp"
+
+void CoreConfiguration(LayerTestsUtils::LayerTestsCommon* test) {
+}

docs/template_plugin/tests/functional/plugin_config.cpp

@@ -1,8 +0,0 @@
-// Copyright (C) 2020 Intel Corporation
-// SPDX-License-Identifier: Apache-2.0
-//
-
-#include "functional_test_utils/plugin_config.hpp"
-
-void PreparePluginConfiguration(LayerTestsUtils::LayerTestsCommon* test) {
-}