Refactor: move Kafka and Pulsar clients to nar files

[eolivelli]

Summary:

• the Pulsar client and the Kafka client import too many third party deps into the main classpath
• move all the clients to .nar files
• split the langstream-kafka and langstream-pulsar modules into two (langstream-kafka-runtime and langstream-pulsar-runtime)
• move the "deploy" and "delete" operations of the StreamingCluster (that is executed on the planner) interface to TopicsConnectionRuntime (that contains the client)
• reworked the loading of the "custom jars", the additional jars must be loaded on a classloader that is on top of the NarClassloader, otherwise the Kafka Connect adapters will try to load the Kafka client and the Kafka Connect APIs from the Connectors (if they bundled them by mistake)