Add new environments folder for Ansible

Closes https://gitlab.com/gitlab-org/quality/gitlab-environment-toolkit/-/issues/148

MR adds a new config folder to Ansible, environments, that will be more flexible for us and users moving forward and our future plans - specifically being able to pass in custom files per environment.

Current users can still use the previous inventories folder for the forseeable but will be encouraged to use environments from now on.