CoreImpl small refactoring (#16145)

* Small CoreImpl refactoring

* Removed cache_dirhandling from CPU plugin

* clang-format

* Fixed python tests

* Fix

* Fixed bugs in HETERO case

* Fixed clang-format and warnings in auto plugin

* Added import_export as capability for TEMPLATE plugin

* Commented throw exception from loaded_from_cache

* Fixed clang-formatof ro template plugin

src/plugins/auto/plugin.cpp

@@ -516,7 +516,6 @@ IExecutableNetworkInternal::Ptr MultiDeviceInferencePlugin::LoadNetworkImpl(cons
     DeviceMap<SoExecutableNetworkInternal> executableNetworkPerDevice;
     std::mutex load_mutex;
     std::vector<Task> loads;
-    std::once_flag readNetworkFlag;
 
     auto loadInferEngTask = [&](DeviceInformation& p) {
         auto tmpiter = fullConfig.find(CONFIG_KEY(ALLOW_AUTO_BATCHING));