Moves all backup chunk-model related classes over to the framework.

Includes the proto definition of ChunksMetadata and related classes.

Some additional changes (apart from style) were needed:
- EncryptedChunkOrdering was modified to be a non-AutoValue class, and
tests were added.
- Protos are now read from an InputStream manually, as any protos should not
be used directly in the platform.
- Helper classes are added for reading from ProtoInputStream.

Bug: 111386661,116575321
Test: atest RunFrameworksServicesRoboTests
Change-Id: I8b74ad059d72e305be7817f79f8c61aa50f7b268