A simplified way of adjusting Spring Cloud LoadBalancer config

[OlgaMaciaszek]

Think of an easier way of switching between ServiceInstanceListSupplier and ReactorLoadBalancer implementations, without the users having to create hierarchies of delegate beans in custom configs.

[spencergibb]

A couple of ideas: a few predefined hierarchies enabled by a property, or a property that is a list of classes and we enable to hierarchy using reflection.

[OlgaMaciaszek]

Adding a builder API and preselected configurations backed by properties.

[OlgaMaciaszek]

Done.