Feature Request: Specify loadBalancer ip for future loadbalancers (not just subnet)

`loadbalancer.openstack.org/load-balancer-address` looks like it is [automatically added](https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/openstack-cloud-controller-manager/expose-applications-using-loadbalancer-type-service.md#service-annotations) and cannot be explicitly set

There does does not seem a way to set it up simialr to subnet-id under LoadBalancer in cloud.conf or `loadbalancer.openstack.org/subnet-id` in the service annotations.

Start with the cloud.conf LoadBalancer settings and the service annotations documented in the linked expose-applications guide, comparing the existing subnet-id handling with loadbalancer.openstack.org/load-balancer-address. Done means users can explicitly provide a load-balancer IP through cloud.conf or a service annotation, with the precedence and supported configuration documented.

Written by the indexing model from the issue text.