Add a brotli decompressor in bsdiff

This CL implements the brotli decompressor used in PatchReader. Also
extract the CompressorType and patch's MagicHeader to a common header file.

Bug: 34220646
Test: Run bsdiff/bspatch with brotli compressor/decompressor over a list
of files from angler's system image.

Change-Id: I76e11168075c6481490ffbc025ec4ca81e828732
13 files changed