cdc: test Kafka network connectivity from nodes

**Is your feature request related to a problem? Please describe.**

Changefeed users may have network connectivity problems from CRDB to Kafka. This is difficult to troubleshoot. The error returned is often `kafka: client has run out of available brokers to talk to (Is your cluster reachable?)`, which I understand to result from any network problem.

Further, Cloud users do not have network troubleshooting tools (`ping`, `nslookup`, `traceroute`) because they can’t `ssh` into Cloud nodes. And, they don’t have access to logs, where they might `cat *.log | grep sarama`.

Problems might also include certs and auth.

**Describe the solution you'd like**

The ability to test Kafka connectivity from the CRDB process, via the SQL client. The Disaster Recovery team has implemented similar for cloud storage: https://github.com/cockroachdb/cockroach/pull/97517

The solution may be an extension of the above to accept `kafka://` URLs. We’d need some way to generate Kafka-specific workload.

See also kcat for inspiration: https://docs.confluent.io/platform/current/clients/kafkacat-usage.html

We might go further and add things like `WITH dns, traceroute, ping` etc, which would not be Kafka-specific. And then iterate on other sinks such as webhook and pubsub.

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Possbile duplicate of https://github.com/cockroachdb/cockroach/issues/60178

Jira issue: CRDB-25245
Epic CRDB-6667