[Developer Experience] Improve configuration discoverability and intellisense

[yuce]

The discoverability and editor intellisense support for hazelcast.config._Config is pretty good, but currently there's not an easy way to pass a _Config object to HazelcastClient.

The easiest solution would be exposing _Config in an experimental fashion and allow passing an instance of it to HazelcastClient instance while keeping the **kwargs of HazelcastClient.