Replace Ingress with Gateway API

[ksuderman]

An initial attempt at what may be required to replace the Nginx Ingress controller with the Gateway API. See the GATEWAY_API_SUMMARY.md and GATEWAY_API_MIGRATION.md files for a more detailed explanation of the changes.

These will not be breaking changes until we set gateways.enabled: true (or ingress.enabled:false) as the default. The current default is gateway.enabled: false