Vultr: Introducing vr_user_facts module (#42951)

This commit introduces a new module called vr_user_facts.

This module aims to return the list of user avaiable avaiable in Vultr.

Sample available here:

```
"vultr_user_facts": [
  {
    "acls": [],
    "api_enabled": "yes",
    "email": "mytestuser@example.com",
    "id": "a235b4f45e87f",
    "name": "mytestuser"
  }
]
```

test/legacy/roles/vr_user_facts/defaults/main.yml

@@ -0,0 +1,8 @@
+user_name: mytestuser
+user_email: mytestuser@example.com
+user_password: aP4ssw0rd!
+user_acls:
+  - upgrade
+  - dns
+  - manage_users
+  - subscriptions

test/legacy/roles/vr_user_facts/tasks/main.yml

@@ -0,0 +1,31 @@
+# Copyright (c) 2018, Yanis Guenane <yanis+ansible@guenane.org>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+---
+- name: Create the user
+  vr_user:
+    name: '{{ user_name }}'
+    email: '{{ user_email }}'
+    password: '{{ user_password }}'
+    acls: '{{ user_acls }}'
+
+- name: test gather vultr user facts in check mode
+  vr_user_facts:
+  check_mode: yes
+
+- name: verify test gather vultr user facts in check mode
+  assert:
+    that:
+    - ansible_facts.vultr_user_facts|selectattr('name','equalto','{{ user_name }}') | list | count == 1
+
+- name: test gather vultr user facts
+  vr_user_facts:
+
+- name: verify test gather vultr user facts
+  assert:
+    that:
+    - ansible_facts.vultr_user_facts|selectattr('name','equalto','{{ user_name }}') | list | count == 1
+
+- name: Delete the user
+  vr_user:
+    name: '{{ user_name }}'
+    state: absent

test/legacy/vultr.yml

@@ -18,3 +18,4 @@
     - { role: vr_ssh_key_facts, tags: test_vr_ssh_key_facts }
     - { role: vr_startup_script, tags: test_vr_startup_script }
     - { role: vr_user, tags: test_vr_user }
+    - { role: vr_user_facts, tags: test_vr_user_facts }