Support configuring Envoy Service loadBalancerSourceRanges/loadBalancerClass via ContourDeployment

**Please describe the problem you have**
When using Contour Gateway Provisioner with a `GatewayClass` that references a custom `ContourDeployment`, it currently does not expose any fields to configure the Envoy Service’s `spec.loadBalancerSourceRanges` or `spec.loadBalancerClass`.

Because of this, we cannot:

- Restrict source IPs at the load balancer level (loadBalancerSourceRanges)

- Select a specific load balancer implementation (loadBalancerClass)

It would be helpful if `ContourDeployment` allowed configuring these two fields so that the Envoy Service can be fully managed through the `GatewayClass` parameters.

Start by locating the ContourDeployment definition and the code that creates the Envoy Service for Gateway Provisioner deployments. Check the related Gateway Provisioner or service-generation tests before making changes. Done means both requested fields can be configured through ContourDeployment and are reflected in the generated Service, with coverage for each field.

Written by the indexing model from the issue text.