Istio packages: update to meet standards

Istio (controlplane):

• Nested folder, should be moved to top level istio
• Gitrepo renamed to istio
• Label update app.kubernetes.io/name: istio (ensure that this does not affect network policies, leave this as-is if it has effects on NPs)
• Namespace STAYS as istio-system

Istio (operator):

• Rename values key to istioOperator
• Nested folder, should be moved to top level istio-operator

NOTE: Values changes and folder changes will require pipeline updates. One example of the type of additions that might be required is big-bang/pipeline-templates/pipeline-templates@f7b639fb