Add other client extensions

[mtmk]

Refactor to use interfaces for enhanced flexibility and testability across various components like NatsJSContext and NatsConnection. Added new extension methods to easily create contexts for Object Store, Key-Value Store, and Services on NATS client and connection instances.

await using var client = new NatsClient();

// Use KeyValueStore extension method by referencing NATS.Client.KeyValueStore package
INatsKVContext kv = client.CreateKeyValueStoreContext();

// Use ObjectStore extension method by referencing NATS.Client.ObjectStore package
INatsObjContext obj = client.CreateObjectStoreContext();

// Use Services extension method by referencing NATS.Client.Services package
INatsSvcContext svc = client.CreateServicesContext();

• fixes INatsClient KV API extensions #613
• fixes INatsClient Object Store API extensions #614
• fixes INatsClient Services API extensions #615

[rickdotnet]

🙌 looking forward to this!

[rickdotnet]

LGTM. All comments are thought provoking.