New SplitPatchWriter to split a bsdiff patch into multiple ones.

This new PatchWriterInterface derived class allows to split the
output patch of a bsdiff run into multiple files of a fixed new file
size. This allows to split long operations with minimal loss of patch
size due to splitting the compression blocks. For large enough new file
sections, this patch size reduction should be minimal.

Bug: 34220646
Test: Added unittests.
Change-Id: Ib90fddd5c55a38c87ce396f2792aa558ecd07b22