Allow sending logs to a non-SG-managed Fluentd instance

The SGDistributedLogs allows to create a pod with Fluentd and Postgres that receives the logs from the Fluentbit sidecar running in all SGCluster pods configured to use distributed logs. SG injects the appropriate configuration to the Fluentbits to point to the correct Fluentd instance.

However, we might consider the option where users may want to not consume the logs directly via the SGDistributedLogs. Since Fluentd is a quite flexible system, users may be able to setup their own Fluentd, with whatever plugins and configuration. Under this scenario we might just inject to the Fluentbit a different Fluentd server configuration, and that's it. We would not manage the distributed logs in this case.