Ports DiffScriptBackupWriter from gmscore to AOSP.

A few additional changes (apart from style and usual dependencies) were
needed:
- Additional dependencies (not part of Backup & Restore code) were
ported over:
	- ByteRange
	- DiffScriptWriter
	- OutputStreamWrapper
	- SingleStreamDiffScriptWriter

- DiffScripBackupWriter.ENCRYPTION_DIFF_SCRIPT_MAX_CHUNK_SIZE_BYTES is
now a constant rather than a flag.
- Additional tests were added for SingleStreamDiffScriptWriter.

Bug: 111386661
Test: atest RunBackupFrameworksServicesRoboTests
Change-Id: Ia3234bb8d665211e6fa91d6a92d190171b0d2dc1