[test coverage] Add tests for set_stats (#74243)

* satisfy the all-knowing, ever present God of Sanity and use 'grep -c' vs. 'wc -l'

test/integration/targets/set_stats/aliases

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+shippable/posix/group5

test/integration/targets/set_stats/runme.sh

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+#!/usr/bin/env bash
+
+set -eux
+
+export ANSIBLE_SHOW_CUSTOM_STATS=yes
+
+# Simple tests
+ansible-playbook test_simple.yml
+
+# This playbook does two set_stats calls setting my_int to 10 and 15.
+# The aggregated output should add to 25.
+output=$(ansible-playbook test_aggregate.yml | grep -c '"my_int": 25')
+test "$output" -eq 1

test/integration/targets/set_stats/test_aggregate.yml

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+---
+- hosts: localhost
+  gather_facts: false
+  tasks:
+      - name: First set_stats
+        set_stats:
+            data:
+                my_int: 10
+
+      - name: Second set_stats
+        set_stats:
+            data:
+                my_int: 15

test/integration/targets/set_stats/test_simple.yml

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+---
+- hosts: localhost
+  gather_facts: false
+  tasks:
+    - name: test simple data with defaults
+      set_stats:
+          data:
+              my_int: 42
+              my_string: "foo"
+      register: result
+
+    - name: assert simple data return
+      assert:
+          that:
+              - result is succeeded
+              - not result.changed
+              - '"ansible_stats" in result'
+              - '"data" in result.ansible_stats'
+              - result.ansible_stats.data.my_int == 42
+              - result.ansible_stats.data.my_string == "foo"
+              - '"per_host" in result.ansible_stats'
+              - not result.ansible_stats.per_host
+              - '"aggregate" in result.ansible_stats'
+              - result.ansible_stats.aggregate
+
+    - name: test per_host and aggregate settings
+      set_stats:
+          data:
+              my_int: 42
+          per_host: yes
+          aggregate: no
+      register: result
+
+    - name: assert per_host and aggregate changes
+      assert:
+          that:
+              - result is succeeded
+              - not result.changed
+              - '"ansible_stats" in result'
+              - '"per_host" in result.ansible_stats'
+              - result.ansible_stats.per_host
+              - '"aggregate" in result.ansible_stats'
+              - not result.ansible_stats.aggregate
+
+    - name: Test bad call
+      block:
+        - name: "EXPECTED FAILURE - test invalid data type"
+          set_stats:
+              data:
+                  - 1
+                  - 2
+
+        - fail:
+            msg: "should not get here"
+      rescue:
+          - assert:
+              that:
+                  - ansible_failed_task.name == "EXPECTED FAILURE - test invalid data type"
+                  - ansible_failed_result.msg == "The 'data' option needs to be a dictionary/hash"
+
+    - name: Test options from template
+      set_stats:
+          data:
+              my_string: "foo"
+          aggregate: "x"
+
+    - name: Test bad data
+      block:
+          - name: "EXPECTED FAILURE - bad data"
+            set_stats:
+                data:
+                    .bad: 1
+          - fail:
+              msg: "should not get here"
+      rescue:
+          - assert:
+              that:
+                  - ansible_failed_task.name == "EXPECTED FAILURE - bad data"
+                  - ansible_failed_result.msg == "The variable name '.bad' is not valid. Variables must start with a letter or underscore character, and contain only letters, numbers and underscores."