[RabbitMQ]: configure timeout for management API requests

### Integration Name

RabbitMQ Logs and Metrics [packages/rabbitmq]

### Dataset Name

_No response_

### Integration Version

1.22.0

### Agent Version

9.5.0

### OS Version and Architecture

n/a

### User Goal

When polling the management API, and especially for larger datasets like the `queues` metrics, the hard-coded timeout of 10 seconds is not enough. We should surface a default or advanced option in the UI to configure a timeout value.

### Existing Features

It is currently not possible to set the timeout in the UI.

### What did you see?

```
Error fetching data for metricset rabbitmq.queue: error in fetch: error making http request:
Get "https://[host]/api/queues": context deadline exceeded
(Client.Timeout exceeded while awaiting headers)
```

### Anything else?

_No response_

Start in packages/rabbitmq and trace how the management API request timeout is defined and exposed to the integration UI. Confirm how the existing 10-second timeout is applied, then verify that a configured value is used for larger requests such as /api/queues without the request timing out.

Written by the indexing model from the issue text.