Panos/doc fragment (#37696)

* Create PanOS module documentation fragment

- Module documentation fragment currently holds 3 parameters
- It most likely won't be used in every single module since there is
some variance

* Modified PanOS module for use doc_frags

- Where documentation is consistent, module documentation now uses a
documentation fragment instead of all documentation being contained in
the module.

* Formatting and syntax error fixes

Updated some formatting errors to make ansibot happy.

* Revisions for grammar

lib/ansible/modules/network/panos/panos_interface.py

@@ -37,18 +37,6 @@ requirements:
 notes:
     - Checkmode is not supported.
 options:
-    ip_address:
-        description:
-            - IP address (or hostname) of PAN-OS device being configured.
-        required: true
-    username:
-        description:
-            - Username credentials to use for auth.
-        default: "admin"
-    password:
-        description:
-            - Password credentials to use for auth.
-        required: true
     if_name:
         description:
             - Name of the interface to configure.
@@ -66,6 +54,7 @@ options:
         description:
             - Commit if changed
         default: true
+extends_documentation_fragment: panos
 '''
 
 EXAMPLES = '''