Resolve "Configure and validate that istiod pulls images from registry1"

General MR

Summary

• Adds imagePullSecret private-registry to the chart/values.yaml.
• Sets the image registry to registry1.dso.mil for all pods in the istio-system and istio-ingress namespaces.

Relevant logs/screenshots

Chart/value.yaml additions were validated in a test k3d cluster.

Linked Issue

#12 (closed)

Upgrade Notices

N/A

Closes #12 (closed)