[Policy Assistant] Avoid unnecessary api calls to get all the pods in the namespace.

[gabrielggg]

When calling functions that use the translate func (for example DeploymentsToTrafficPeers func), we are getting all the pods on the namespace one time per each deployment on that specific namespace , so that is not correct. Ideally, we'd get all pods in the namespace only once.

Example code snippet from DeploymentsToTrafficPeers func to take as reference (source file: https://github.com/kubernetes-sigs/network-policy-api/blob/main/cmd/policy-assistant/pkg/matcher/traffic.go):

for _, deployment := range kubeDeployments {
			tmpInternalPeer := InternalPeer{
				Workload: namespace.Name + "/deployment/" + deployment.Name,
			}
			tmpPeer := TrafficPeer{
				Internal: &tmpInternalPeer,
			}
			tmpPeerTranslated := tmpPeer.Translate() //here we are calling the translate func inside a loop and 
                        //the translate func is making the same api call to the api server multiple times
			if tmpPeerTranslated.Internal.Workload != "" {
				deploymentPeers = append(deploymentPeers, tmpPeerTranslated)
			}

		}

And inside the translate func we are doing this call:

 utils.DoOrDie(err)
 ns, err := kubeClient.GetNamespace(workloadMetadata[0])
 utils.DoOrDie(err)
 kubePods, err := kube.GetPodsInNamespaces(kubeClient, []string{workloadMetadata[0]})

Originally posted by @huntergregory in https://github.com/kubernetes-sigs/network-policy-api/pull/227#discussion_r1645048124