Create BackupAnnotations for B&R-related annotations and constants

The class will serve as a container for B&R-specific logical types that
are used throughout the code base (i.e. including non-BR components).

Replace BackupManager#OperationType with the new
BackupAnnotations#BackupDestination.

Bug: 255376040
Test: m -j
Change-Id: Ica9fc4670575dab01dbf18864cd8e5ec1132738f