an ini to load. Only reading from it if it exists. If this is relative, this function will try both in getcwd and in the instance.cwd, if an instance is set.
if true, don't attempt to override the given ini with workspace-d user configs.
default D-Scanner configuration to use if no user config exists (workspace-d specific or ini argument)
Gets the used D-Scanner config, optionally reading from a given dscanner.ini file.