Org Mover: Implement selective sync scope for DependencyProxy::Blob

Problem

We need to implement selective sync by organization: &17004. We can break up the work by data type.

Proposal

Implement the selective sync scope for the DependencyProxy::Blob model.

Prerequisites

• dependency_proxy_blobs has a sharding key

If #514251 (closed) is not yet done, then implement a stub for GeoNode.selective_sync_by_organizations? which always returns false)

Acceptance criteria

When selective sync by organization is selected, then blobs will be selectively synced on the secondary site, and selectively checksummed on the primary site.