Clean up module documentation (#36909)

* Clean up module documentation

This PR includes:
- Removal of `default: None` (and variations)
- Removal of `required: false`
- Fixing booleans and `type: bool` where required

* Fix remaining (new) validation issues

lib/ansible/modules/cloud/openstack/os_nova_host_aggregate.py

@@ -28,16 +28,10 @@ options:
     required: true
   metadata:
     description: Metadata dict.
-    required: false
-    default: None
   availability_zone:
     description: Availability zone to create aggregate into.
-    required: false
-    default: None
   hosts:
     description: List of hosts to set for an aggregate.
-    required: false
-    default: None
   state:
     description: Should the resource be present or absent.
     choices: [present, absent]