Bugfixes and integration tests for 'default' callback plugin

* display 'changed' tasks when hiding 'ok' tasks
* display proper task title for handlers (fixes #44007)

test/integration/targets/callback_default/test.yml

@@ -0,0 +1,60 @@
+---
+- hosts: testhost
+  gather_facts: no
+  vars:
+    foo: foo bar
+  tasks:
+    - name: Changed task
+      command: echo foo
+      changed_when: true
+      notify: test handlers
+
+    - name: Ok task
+      command: echo foo
+      changed_when: false
+
+    - name: Failed task
+      fail:
+        msg: no reason
+      ignore_errors: yes
+
+    - name: Skipped task
+      command: echo foo
+      when: false
+
+    - name: Task with var in name ({{ foo }})
+      command: echo foo
+
+    - name: Loop task
+      command: echo foo
+      loop:
+        - 1
+        - 2
+        - 3
+      loop_control:
+        label: foo-{{ item }}
+  handlers:
+    - name: Test handler 1
+      command: echo foo
+      listen: test handlers
+
+    - name: Test handler 2
+      command: echo foo
+      changed_when: false
+      listen: test handlers
+
+    - name: Test handler 3
+      command: echo foo
+      listen: test handlers
+
+# An issue was found previously for tasks in a play using strategy 'free' after
+# a non-'free' play in the same playbook, so we protect against a regression.
+- hosts: testhost
+  gather_facts: no
+  strategy: free
+  tasks:
+    - name: First free task
+      command: echo foo
+
+    - name: Second free task
+      command: echo foo