Include dependency role names in role_names. (#46483)

* -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.

test/integration/targets/special_vars/tasks/main.yml

@@ -23,7 +23,7 @@
   include_vars: "{{output_dir}}/special_vars.yaml"
 
 
-- name: veriy all test vars are defined
+- name: verify all test vars are defined
   assert:
     that:
         - 'item in hostvars[inventory_hostname].keys()'
@@ -35,3 +35,24 @@
     - test_template_fullpath
     - test_template_run_date
     - test_ansible_managed
+
+- name: ensure that role_name exists in role_names, ansible_play_role_names, ansible_role_names, and not in ansible_dependent_role_names
+  assert:
+    that:
+      - "role_name in role_names"
+      - "role_name in ansible_play_role_names"
+      - "role_name in ansible_role_names"
+      - "role_name not in ansible_dependent_role_names"
+
+- name: ensure that our dependency (prepare_tests) exists in ansible_role_names and ansible_dependent_role_names, but not in role_names or ansible_play_role_names
+  assert:
+    that:
+      - "'prepare_tests' in ansible_role_names"
+      - "'prepare_tests' in ansible_dependent_role_names"
+      - "'prepare_tests' not in role_names"
+      - "'prepare_tests' not in ansible_play_role_names"
+
+- name: ensure that ansible_role_names is the sum of ansible_play_role_names and ansible_dependent_role_names
+  assert:
+    that:
+      - "(ansible_play_role_names + ansible_dependent_role_names)|unique|sort|list == ansible_role_names|sort|list"