[Enhancement] Add poll duration config for UI Stream

### Request Type
Enhancement

### Problem Description
The goal of this issue is to:

- [x] add a `stream.longPolling.pollingDuration` property to define the `amount of time the UI have to wait before polling the stream`
- [x] add the `pollingDuration` to the output of `GET /api/status` API
- [x] set the default value to `1 seconds`