Merge gateway EnvoyProxy parameters between the class and gateway instance

Description: When using a set of EnvoyProxy parameters at the gateway class level with spec.parametersRef and a separate set of parameters at the gateway level with spec.infrastructure.parametersRef, it would be nice if the configuration was merged and the gateway parameters override the gateway class parameters. For example, I want to setup the gateway class to set a default replica count of two and a PDB with minAvailable=1 for all my gateways and setup my gateways with specific loadBalancerIPs.

The Gateway API does call this feature out as implementation specific and includes a recommendation for this support but through testing of Envoy Gateway v1.1.0 gateway instance parameters seem to override all gateway class parameters.

Relevant Links: https://gateway-api.sigs.k8s.io/reference/spec/#gateway.networking.k8s.io/v1.GatewayClassSpec https://gateway-api.sigs.k8s.io/reference/spec/#gateway.networking.k8s.io/v1.GatewayInfrastructure