[occm] Ability to select lb-provider in annotations

[MaximMonin]

Is this a BUG REPORT or FEATURE REQUEST?:

/kind feature

What happened:
At the moment, the lb-provider option is set via cloud config. And so it works for all registered services. At the moment, lb-provider ovn is almost functional, but when used in services with the externalTrafficPolicy: Local option, on some installations it has problems updating the traffic routing table, which can cause it to hang. But when the service is present on all worker nodes, this problem does not occur. So we would like to be able to use lb-provider ovn for some services, even if the default provider is amphora.

What you expected to happen:
I would like to add new annotation to service.

apiVersion: v1
kind: Service
metadata:
  annotations:
    loadbalancer.openstack.org/lb-provider: ovn
    loadbalancer.openstack.org/lb-method: SOURCE_IP_PORT
  name: nginxsvc
  labels:
    app: nginx
spec:
  type: LoadBalancer
  ports:
  - port: 80
    protocol: TCP
    name: http
  selector:
    app: nginx

How to reproduce it:
Anything else we need to know?:
Environment:

• openstack-cloud-controller-manager(or other related binary) version: 1.30.1
• OpenStack version: 2023.1