SPIKE: Explore Gateway API as replacement for istio gateways

Motivation

Istio's own documentation makes clear that Gateway API provides most of the machinery necessary to configure ingress and egress gateways for Istio. The purpose of this spike is to identify the gaps gateway API does not cover and to determine if those gaps are cause for concern with regard to how Big Bang uses Istio gateways.

Acceptance Criteria

• A full breakdown of the features supported by Istio but not exposed via the k8s-native Gateway API must be commented on this issue
• A PoC branch with Gateway API standing in for Istio gateways must be created and linked back to this issue
• The findings from this spike must be presented to the team and anchors to identify the path forward