scripted-diff: Modify unit tests to use the ArgsManager in the BasicTestingSetup class instead of implicitly relying on gArgs.

-BEGIN VERIFY SCRIPT-
git ls-files src/test/dbwrapper_tests.cpp src/test/denialofservice_tests.cpp src/test/flatfile_tests.cpp src/test/fs_tests.cpp src/test/settings_tests.cpp src/test/util_tests.cpp | xargs sed -i 's/GetDataDir()/m_args.GetDataDirPath()/g';
-END VERIFY SCRIPT-

src/test/settings_tests.cpp

@@ -45,7 +45,7 @@ BOOST_FIXTURE_TEST_SUITE(settings_tests, BasicTestingSetup)
 
 BOOST_AUTO_TEST_CASE(ReadWrite)
 {
-    fs::path path = GetDataDir() / "settings.json";
+    fs::path path = m_args.GetDataDirPath() / "settings.json";
 
     WriteText(path, R"({
         "string": "string",