Implement Report persistency

Now Report properties are stored in non-volatile memory. It allows
to restore Report after system restart. Persistency of a report is
controlled by Persistency property in Report interface.

Tested:
 - Passed unit tests
 - Verified that report is stored in /var/lib/telemetry dir
 - Verified that report is restored from storage after telemetry
   service start

Signed-off-by: Wludzik, Jozef <jozef.wludzik@intel.com>
Change-Id: Iccfe21603eecffc4e174a4403f699b03de320db9
diff --git a/tests/src/mocks/json_storage_mock.hpp b/tests/src/mocks/json_storage_mock.hpp
index 99ecd41..ab76459 100644
--- a/tests/src/mocks/json_storage_mock.hpp
+++ b/tests/src/mocks/json_storage_mock.hpp
@@ -10,8 +10,8 @@
     MOCK_METHOD(void, store, (const FilePath&, const nlohmann::json&),
                 (override));
     MOCK_METHOD(bool, remove, (const FilePath&), (override));
+    MOCK_METHOD(bool, exist, (const FilePath&), (const, override));
     MOCK_METHOD(std::optional<nlohmann::json>, load, (const FilePath&),
                 (const, override));
-    MOCK_METHOD(std::vector<FilePath>, list, (const DirectoryPath&),
-                (const, override));
+    MOCK_METHOD(std::vector<FilePath>, list, (), (const, override));
 };