Implemented the diffbased entity insertion approach guarded by the `diffbasedEntityInsertion` Arcs Flag.

[copybara-service[bot]]

Implemented the diffbased entity insertion approach guarded by the diffbasedEntityInsertion Arcs Flag.

The diffbased approach fetches all the entity reference ids from the collection table and compares them to the updated collection to determine which entities to add/remove from the collection.