The `test/integration/integration_config.yml` vars file will now be loaded from the content under test and is now optional.
The `output_dir` and `win_output_dir` vars are now provided by ansible-test.
* Move Ansible test config into env vars.
This allows ansible-test to use an empty Ansible config file, leaving open the option for users to customize the one used to run tests (although such usage is discouraged).
* Use config from content under test when present.