Nexus - Add Dynamic Network Policy support

Description:

Currently many Ingress and Egress package network policies have hardcoded namespaceSelector labels. These hardcoded labels do not support the migration to Istio Operator-less deployments. This issue will track adding support for namespaceSelector labels that are dynamically passed from the Big Bang umbrella chart.

Implementation Guide Tasks:

• Setup Network Policies for Dynamic Values
• Validate Changes in a K3d Cluster with BB deployed and Istio Operator enabled
• Validate Changes in a K3d Cluster with BB deployed and Istio Operator-less (istioCore) enabled
• Add Required Templating in Big Bang Merge request