Implement NETCONF OpenConfig collector for pluggable optical-channel metrics
- Add NetconfOpenConfigCollector class to handle NETCONF-over-SSH connections and metrics collection. - Introduce KPI enumeration for optical-channel metrics. - Create PathBuilder for constructing NETCONF filter XML and parsing responses. - Add unit tests for NetconfOpenConfigCollector functionality. - Update requirements to include ncclient for NETCONF operations. - Enhance HelperMethods with new subscription handling for pluggable KPIs.