[core] Preserve timestamp values on changelog retraction records

[junmuz]

Purpose

• Adds a new config option changelog-producer.preserve-sequence-on-retract that accepts a comma-separated list of column names whose values should be taken from the incoming event (rather than the stored row) when producing changelog retraction records (-U, -D)
• This is useful when delete or update events carry an event timestamp that downstream consumers need — e.g., external systems like Cassandra that rely on WRITETIME for conflict resolution
• Only supported with the lookup changelog producer

Tests

• Unit tests for delete retraction preserving the event's sequence field value
• Unit tests for update retraction (-U) carrying the new event's sequence field value
• Unit tests confirming original behavior is preserved when the option is not set