Add support fot Gateway API GRPCRoute

[vspallas-flyr]

Hi,

Only the HTTPRoute is supported from the Gateway API. Why is the GRPCRoute not? I show a comment https://github.com/FLYR-Open-Source/open-feature-operator/blob/5358d1eacfd44cf01016c4bc6f68c496e757354f/internal/controller/core/flagd/resources/gateway_api.go#L100-L102, but I don't understand what it means. What is the GRPC gateway? Also, in my case, I would like to create both an HTTPRoute and a GRPCRoute for different hostnames.

I can raise a PR to include the GRPCRoute as well.