Support new Gateway API v1.3 fields

[rg0now]

The new Gateway API version allows to associate labels/annotations directly via the Gateway spec and also to specify the parameters reference (i.e., the GatewayConfig) on a per Gateway basis, see here.

Intended behavior:

• if spec.infrastructure.labels is given then merge these labels on top of the ones specified directly on the Gateway, overwriting overlapping labels,
• if spec.infrastructure.annotations is given then merge these annotations on top of the ones specified directly on the Gateway, overwriting overlapping annotations,
• if spec.infrastructure.parametersRef is given and it points to a GatewayConfig in the same namespace as the Gateway then use that GatewayConfig instead of the default one as specified in the GatewayClass. This would also make the parametersRef in the GatewayClass optional.