Ports part of the backup/encryption/chunking code from gmscore.

Some additional changes (apart from style) were needed:
- ChunkOrderingType.java is an @IntDef referencing the possible values
for the ChunkOrderingType enum in the proto.
- EncryptedChunk.java is no longer an AutoValue class.
- Inlined some constants from Guava.

Bug: 111386661,116575321
Test: atest RunFrameworksServicesRoboTests
Change-Id: I7656cae13de0bd918be5016ffb155de4b8fd5f71