Consider using Gateway.spec.infrastructure labels/annotations fields

[jenshu]

Gateways now have an infrastructure field, which allows users to specify labels and annotations to apply to all dynamically provisioned proxy resources. Consider using the new fields instead of, or in addition to, the currently supported GatewayParameters fields.

Things to consider:

• Note that currently, labels and annotations for Pods, Services, and ServiceAccounts can each be configured independently via GatewayParameters, whereas the Gateway.spec.infrastructure field would apply the same set of labels/annotations to all proxy resources. If we use Gateway.spec.infrastructure, should that be considered a base set of labels/annotations for all resources, that can be further customized per-resource via GatewayParameters? Would we merge or overwrite (or should we deprecate/remove the GWP fields and only use infrastructure)?
• There would be a slight UX change, where proxy config would now live in 2 places: labels/annotations would live on the Gateway spec, and other config would live in GatewayParameters. Is this acceptable?