Formalized Multi-cluster and Leafnode toplogies

[ripienaar]

The idea here is to formalize topologies we support and to minimise down the configuration options that users have to supply - rather than use the JetStream structs for those, we reframe things and add KV specific terminology and structs so we can model toplogies rather than plumbing.

TBD here after initial discussions complete is to make some adjustments to the main KeyValue to be able to figure out if a thing is a Aggregate and to get at this config.

[ripienaar]

@jnmoyne and @aricart this is a draft PR lets chat a bit about this

[ripienaar]

Capturing some comments from a call:

• Do not use Replica as its overloading existing term, stick to Mirror its fine really
• We will need to support adding that have hand supplied API prefixes and such since the edge may not have full access to the origin bucket at all to support the bucket orierntated API.