[Feature Request] Add `condition` field to `Custom Filestream Logs` integration in Kibana

## Use Case

As our company's Elastic Cloud admin, I need to be able to apply a condition to custom logs to enable or disable them on specific hosts.

## Description

With the deprecated `Custom Logs` integration, it was possible to add a `condition` to the integration in the `Custom Configurations` field. An example of this would be:

```yaml
condition: '${host.platform} == "linux"'
```

This field is not present in the new `Custom Filestream Logs` integration, and as a result, conditions cannot be set.

> **Note:** This would be a nice feature to have in **all** integrations in Kibana, but is most important for this integration.