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/cloudstack/cs_sshkeypair.py

@@ -41,29 +41,20 @@ options:
   domain:
     description:
       - Domain the public key is related to.
-    required: false
-    default: null
   account:
     description:
       - Account the public key is related to.
-    required: false
-    default: null
   project:
     description:
       - Name of the project the public key to be registered in.
-    required: false
-    default: null
   state:
     description:
       - State of the public key.
-    required: false
     default: 'present'
     choices: [ 'present', 'absent' ]
   public_key:
     description:
       - String of the public key.
-    required: false
-    default: null
 extends_documentation_fragment: cloudstack
 '''