changefeedccl: add duplicate ordering test

Some users rely on changefeeds to be idempotent. That is, if a changefeed emits a duplicate message for a key, all events for that key since the initial duplicate message should also be emitted. This is not a guarantee currently provided by changefeeds, but the only known way in the current implementation to violate this property is fine grain checkpointing. If `changefeed.frontier_checkpoint_frequency` is disabled (to disable fine grain checkpointing), duplicate events should be emitted in order. We should add a test disabling this setting that validates the idempotent duplicates behavior.

Jira issue: CRDB-39516

Epic CRDB-38755