[Fleet] Add force to upgrade openAPI (#138000) (#138023)

(cherry picked from commit 6bd3c73cec)

Co-authored-by: Nicolas Chaulet <nicolas.chaulet@elastic.co>

x-pack/plugins/fleet/common/openapi/components/schemas/bulk_upgrade_agents.yaml

@@ -21,6 +21,9 @@ properties:
         items:
           type: string
         description: list of agent IDs
+  force:
+    type: boolean
+    description: Force upgrade, skipping validation (should be used with caution)
 required:
   - agents
   - version

x-pack/plugins/fleet/common/openapi/components/schemas/upgrade_agent.yaml

@@ -1,16 +1,12 @@
 title: Upgrade agent
-oneOf:
-  - type: object
-    properties:
-      version:
-        type: string
-    required:
-      - version
-  - type: object
-    properties:
-      version:
-        type: string
-      source_uri:
-        type: string
-    required:
-      - version
+type: object
+properties:
+  version:
+    type: string
+  source_uri:
+    type: string
+  force:
+    type: boolean
+    description: Force upgrade, skipping validation (should be used with caution)
+required:
+  - version