housekeeping: Add offloading bucket sink

Repository offloading involves interacting with the offloading storage to handle operations such as downloading, uploading, deleting, and listing objects.

In this MR, we introduce a Sink interface, which defines the essential operations required for interacting with offloading storage. Additionally, a simulation bucket is implemented to inject delays and errors into responses, enabling more robust and comprehensive testing.

Closes #6513 (closed)