[Fleet] Add missing required kbn-xsrf header to API spec (#105858)

## Summary

All mutating HTTP methods (`POST`, `PUT`, `DELETE`) require a `kbn-xsrf` header & value. Found an operation which was missing the requirement.

Only real changes are 98dc5b5fdf (file `/paths/agent_policies@{agent_policy_id}@copy.yaml`. Others will disappear when https://github.com/elastic/kibana/pull/105824 lands in master

### Checklist

- [x] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials

x-pack/plugins/fleet/common/openapi/bundled.json

@@ -941,6 +941,11 @@
       "post": {
         "summary": "Agent policy - copy one policy",
         "operationId": "agent-policy-copy",
+        "parameters": [
+          {
+            "$ref": "#/components/parameters/kbn_xsrf"
+          }
+        ],
         "responses": {
           "200": {
             "description": "OK",
@@ -981,8 +986,7 @@
             }
           },
           "description": ""
-        },
-        "description": "Copies one agent policy"
+        }
       }
     },
     "/agent_policies/delete": {

x-pack/plugins/fleet/common/openapi/bundled.yaml

@@ -579,6 +579,8 @@ paths:
     post:
       summary: Agent policy - copy one policy
       operationId: agent-policy-copy
+      parameters:
+        - $ref: '#/components/parameters/kbn_xsrf'
       responses:
         '200':
           description: OK
@@ -604,7 +606,6 @@ paths:
               required:
                 - name
         description: ''
-      description: Copies one agent policy
   /agent_policies/delete:
     post:
       summary: Agent policy - Delete

x-pack/plugins/fleet/common/openapi/paths/agent_policies@{agent_policy_id}@copy.yaml

@@ -7,6 +7,8 @@ parameters:
 post:
   summary: Agent policy - copy one policy
   operationId: agent-policy-copy
+  parameters:
+    - $ref: ../components/headers/kbn_xsrf.yaml
   responses:
     '200':
       description: OK
@@ -32,4 +34,4 @@ post:
           required:
             - name
     description: ''
-  description: Copies one agent policy
+