config: Use disambiguated interface names

[efritz]

- filename: internal/codeintel/uploads/mocks_test.go
  sources:
    - path: github.com/sourcegraph/sourcegraph/internal/codeintel/uploads/internal/store
      interfaces:
        - Store
    - path: github.com/sourcegraph/sourcegraph/internal/codeintel/uploads/internal/lsifstore
      interfaces:
        - LSIFStore
    - path: github.com/sourcegraph/sourcegraph/internal/codeintel/uploads
      interfaces:
        - GitserverClient
    - path: github.com/sourcegraph/sourcegraph/internal/workerutil/dbworker/store
      interfaces:
        - Store
      prefix: Worker

This is currently illegal, although it would generate non-conflicting code. This should be accepted when using non-command-line flags.