[elicitations] Switch to use MCP style elicitation payload for mcp tool approvals. (#13621)

- [x] Switch to use MCP style elicitation payload for mcp tool
approvals.
- [ ] TODO: Update the UI to support the full spec.

codex-rs/app-server-protocol/schema/json/McpServerElicitationRequestResponse.json

@@ -11,6 +11,9 @@
     }
   },
   "properties": {
+    "_meta": {
+      "description": "Optional client metadata for form-mode action handling."
+    },
     "action": {
       "$ref": "#/definitions/McpServerElicitationAction"
     },