Create blog post explaining incoming istio changes

Motivation

Operatorless istio will arrive in Big Bang with many architectural changes to the way gateways are deployed. A blog post would service the transition well and would help customers bridge the gap between operatorful and operatorless istio configuration.

Acceptance Criteria

• A blog post is published explaining the transition to operatorless istio with a focus on:
  • Why does this transition need to happen?
  • What are the incompatibilities between current configurations and new configurations?
  • What's the timeline for consumers to make this transition?
  • What steps should they take today?