Allow adding 'config' on the routes added by Swagger-UI

### Prerequisites

- [x] I have written a descriptive issue title
- [x] I have searched existing issues to ensure the feature has not already been requested

### 🚀 Feature Proposal

I want to be able to add stuff to the Fastify route config object for the routes added by the swagger-ui plugin, so I can access the config in request.routeOptions.config

Because this isn't currently possible, I'm resorting to registering an 'onRoute' hook before registering the swagger(-ui) plugins, but this hook then remains and as Fastify doesn't allow removing hooks

### Motivation

_No response_

### Example

_No response_