Update behat_permissions to act as data generators

Currently our steps for the following are all performed via the UI:

• I set the following system permissios of "rolename" role:
• I override the system permissionsn of "rolename" role with:
• I define the allowed role assignments for the "rolename" role as:
• I fill in the allowed role assignments form for the "rolename" role with:

These steps were mostly created in MDL-37958 but I believe that this is the wrong approach.

These steps should be treated as data generators, or possibly even converted to first-class data generators and actually deprecated.

These steps themselves should not be required to use the UI, or log in as an administrator, etc. because they are all setup steps. The only time that this is not the case is when we are actively testing the pages which back these settings, in which case we should be using standard steps.