change_stream_oplog_notification.cpp has 7 notify* functions emitting 8 distinct events

• shardCollection,
• movePrimary,
• reshardCollection,
• namespacePlacementChanged,
• migrateLastChunkFromShard,
• migrateChunkToNewShard,
• moveChunk,
• refineCollectionShardKe

whose o2 payloads are still built with raw BSONObjBuilder / BSON(...).
Three sibling reshard events already use IDL structs from resharding_change_event_o2_field.idl.

Migrate the remaining payloads to IDL types (reusing KeyPattern where applicable) so all notifications follow the same pattern; output BSON must remain byte-equivalent to keep v1/v2 readers happy.

Open question:

• extend the existing IDL file, rename it (e.g. change_stream_event_o2_field.idl) and move it next to the writer in src/mongo/db/repl/, or
• create a new sibling file for the non-resharding events.