feature request: Apigateway REST getExport as Swagger

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-export-api.html

https://github.com/spulec/moto/issues/4888

### 🧑‍💻 Implementation

_No response_

### Anything else?

_No response_