-Add: Test cases for ansible_parent_role_names and ansible_parent_role_paths
-Add: ansible_parent_role_names/paths variables for when a role is being included by another role.
* -Change: Include dependency role names in `role_names`.
-Add: `play_role_names` magic variable to include only explicitly named roles (formerly `role_names`).
-Add: `dependent_role_names` magic variable to include all dependency names for all roles.
* -Change: use the ansible_ prefix for new magic variables.
-Change: keep `role_names` as a deprecated variable, using the old functionality.
* -Add: changelog fragment for the role_names rework.
* -Add: Tests for the role_names (and ansible_*role_names) special variables
* -Fix: resolve erroneous documentation snippet that was introduced after rebasing.
* -Fix: explicitly sort to ensure list comparison works in test.
