Gateway spec conformance test

[Tharsanan1]

Description:
Gateway spec conformance test has core level support and extended level support. To obtain core-level support we need to support the following features

• Gateway
• HTTPRoute
• ReferenceGrant
• TLSRoute

our implementation needs significant changes to support this core level support.

• Need to correctly reconcile Gateway, GatewayClasses, HTTPRoutes and update their statuses based on the spec
• Only accepted HTTPRoutes by the Gateway, should be added envoy configuration.
• Any resources except HTTPRoute that are shared between different namespaces should have a valid ReferenceGrant for this.
• Need to discuss the support of TLSRoute.

I have added the gateway class controller, HTTP route controller, and some validation to the gateway controller in this draft PR: #1833