Include vars updated to work with directories (#17207)

* New features for include_vars

include_vars.py now allows you to include an entire directory and its nested directories of variable files.

Added Features..

* Ignore by default *.md, *.py, and *.pyc
* Ignore any list of files.
* Only include files nested by depth (default=unlimited)
* Match only files matching (valid regex)
* Sort files alphabetically and load in that order.
* Sort directories alphabetically and load in that order.

```
    - include_vars: 'vars/all.yml'

    - name: include all.yml
      include_vars:
        file: 'vars/all.yml'

    - name: include all yml files in vars/all and all nested directories
      include_vars:
        dir: 'vars/all'

    - name: include all yml files in vars/all and all nested directories and save the output in test.
      include_vars:
        dir: 'vars/all'
        name: test

    - name: include all yml files in vars/services
      include_vars:
        dir: 'vars/services'
        depth: 1

    - name: include only bastion.yml files
      include_vars:
        dir: 'vars'
        files_matching: 'bastion.yml'

    - name: include only all yml files exception bastion.yml
      include_vars:
        dir: 'vars'
        ignore_files: 'bastion.yml'
```

* Added whitelist for file extensisions (yaml, yml, json)

* Removed unit tests in favor of integration tests

test/integration/test_include_vars.yml

@@ -0,0 +1,5 @@
+---
+- hosts: 127.0.0.1
+  gather_facts: False
+  roles:
+    - { role: test_include_vars }