eDB: Commit synchronize option with load update

This feature enables synchronous commit operations for the ephemeral database. Starting in 25.4, we've changed the default commit synchronize model for the ephemeral database from the asynchronous model to the synchronous model. The synchronous model provides better assurance that the ephemeral configuration is synchronized across Routing Engines or Virtual Chassis members by processing commits synchronously. With this change, only the synchronous model supports synchronizing ephemeral data on devices that have graceful Routing Engine switchover (GRES) or nonstop active routing (NSR) enabled.