Now that the `ConfigFileFinder` has the `.ignore_config_files`
attribute, switch the relevant code paths to utilize this public
attribute.
Tests have been updated to either construct `ConfigFileFinder` or mock
the object appropriately.
Now that `args` parameters is not being used, it is safe to remove from
the constructor signature.
Further work is required to evaluate and clean-up tearing out the
threading-through of `args` from various callers and tests.
