metrics: Add metrics for v1alpha1 Route types

[david-martin]

• GRPCRoute
  • https://github.com/kubernetes-sigs/gateway-api/blob/main/apis/v1alpha2/grpcroute_types.go
  • https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1alpha2.GRPCRoute
• TCPRoute
  • https://github.com/kubernetes-sigs/gateway-api/blob/main/apis/v1alpha2/tcproute_types.go
  • https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1alpha2.TCPRoute
• TLSRoute
  • https://github.com/kubernetes-sigs/gateway-api/blob/main/apis/v1alpha2/tlsroute_types.go
  • https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1alpha2.TLSRoute
• UDPRoute
  • https://github.com/kubernetes-sigs/gateway-api/blob/main/apis/v1alpha2/udproute_types.go
  • https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1alpha2.UDPRoute

These reuse some of the same types as HTTProute, so the metrics can likely be reused and adapted.