cdc: add observability metrics to throttling behaviour in kafka #117618
Description
We should find a way to add observability into sarama code https://github.com/IBM/sarama/blob/d9abf3cfb14d41fbc059d0f36195603000b1aad2/broker.go#L1695C1-L1696C38 when there is throttling behaviour kafka.
One way is to inject our metrics into sarama's code using metricRegistry https://github.com/IBM/sarama/blob/d9abf3cfb14d41fbc059d0f36195603000b1aad2/async_producer.go#L89.
Part of: #92290
Jira issue: CRDB-35272