New Observability Updates in Confluent Cloud Kafka

Introduces new observability metrics for Confluent Cloud Kafka: `io.confluent.kafka.server/client_limit_milliseconds` to identify users breaching limits and reasons, `io.confluent.kafka.server/max_pending_rebalance_time_milliseconds` to monitor consumer group rebalance duration and frequency, `io.confluent.kafka.server/connection_accept_count` to track connection attempts for elastic cluster scaling, and a new `cleanup.policy` dimension for `io.confluent.kafka.server/partition_count` to differentiate compacted partitions. Also details a refreshed cluster monitoring experience in Confluent Cloud Console.