Use bespoke field for referencing related load balanacers

[strideynet]

At the moment, we set the name of the LB to something predictable and fetch it by listing all LBs for an organisation and manually searching for a match. Eventually, first class support will be added to the Katapult API. This issue is to implement support for that when those changes have been made to the API.

You will need to:

• Remove lb.getLoadBalancer() or adjust it to use the new endpoints
• Come up with a migration strategy that retains support for previously created LoadBalancers