Implement ChangeFeed for offline replication

[alaye-ms]

External work: Need OSS DocumentDB ChangeFeed support first

In the meantime, create a ChangeFeed migration playground using CoPilot generated documentdb ChangeFeed implementation from this branch: https://github.com/xgerman/documentdb/tree/changefeed_vibe/pg_documentdb_gw/src/changestream

Should be able to migrate from an OSS Documentdb k8s pod to an Azure Documentdb instance, and reverse if possible.

Ensure that mid-operation failures can be restarted where they left off.
Conflicts can be logged and ignored for now.

Only specific tables needed, not a full DB migration.

Final result should include a recorded demo of this result.