Add 'tower_settings' module for managing Ansible Tower Settings (#43933)

* add the tower_settings module

test/integration/targets/tower_settings/aliases

@@ -0,0 +1,2 @@
+cloud/tower
+shippable/tower/group1

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

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+- name: Set the value of AWX_PROOT_SHOW_PATHS
+  tower_settings:
+    name: "AWX_PROOT_SHOW_PATHS"
+    value: "'/var/lib/awx/projects/', '/tmp'"
+  register: result
+
+- assert:
+    that:
+      - "result is changed"
+
+- name: Set the value of AWX_PROOT_BASE_PATH
+  tower_settings:
+    name: AWX_PROOT_BASE_PATH
+    value: "/tmp"
+  register: result
+
+- assert:
+    that:
+      - "result.value == '/tmp'"