KafkaSinkCluster: scram_over_mtls broker discovery

[rukai]

progress towards https://github.com/shotover/shotover-proxy/issues/1618

This PR:

• introduces a new integration test cluster_sasl_scram_over_mtls_multi_shotover, previously we just had cluster_sasl_scram_over_mtls_single_shotover
  • This tests with multiple shotover's running which could reveal some edge cases
  • It also uses various numbers of elements in mtls_port_contact_points for each shotover yaml, which will exercise different cases within the broker discovery logic
• Replaces the simple list of connections with a list of nodes.
  • This is needed so we can avoid creating duplicate connections and recreate connections if they go down.
• Adds a find_new_brokers method which performs broker discovery.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #1640 will not alter performance

_{Comparing rukai:token_task_broker_discovery (04296c1) with main (f6c0f46)}

Summary

✅ 37 untouched benchmarks