Remove `listenerOnlyMode` out of guestAgent

[Nino-K]

We should remove the functionality for creating iptables listeners, as we no longer depend on WSL listener forwarding within the virtual network. Additionally, we previously did not invoke the host-switch API for iptables entries, an issue this PR addresses. Furthermore, this PR eliminates the redundant iptables package. Originally, the purpose of scraping iptables was to capture the port mappings from /proc/net/tcp, which were inserted by the CNI portmap plugin. However, we now subscribe directly to the Kubernetes API and obtain all port mappings directly from the API within the kube/watcher package.