tests: Add tests for WpSettings object
- settings.c tests conf file loading & parsing, metadata updates, wpsetttings object creation and its API.
- settings.lua tests the API from lua scripts.
- Add a sample settings.conf file, this file contains sections copied over from client.conf along with the settings section. Add a file each for wp side and lua side of scripts.
- Make changes in base test infrastructure to take a custom conf file.
- Enhance the wp_settings_get_instance_api() to be take metadata_name parameter. So, Wpsetttings is now a singleton instance for a given metadata file.
- Enhance the m-settings module also to be take metadata_name parameter. this is handy for lua side of tests as its cumbersome to do this is lua.