Store a compressed copy of packages.xml.

This is step 1, use JNI call to compress+checksum the backup copy.
Split into 2 steps to detect any issues/benchmark regressions etc.

packages.xml: 461903bytes

GZip compression (204498bytes):
write: 12ms, compress: 21ms
write: 16ms, compress: 70ms
write: 146ms, compress: 48ms
write: 11ms, compress: 46ms
write: 13ms, compress: 54ms
write: 16ms, compress: 57ms
write: 21ms, compress: 74ms
write: 17ms, compress: 94ms
write: 13ms, compress: 77ms
write: 10ms, compress: 56ms
write: 8ms, compress: 48ms

Native LZ4 + checksum (239481bytes), compatible with lz4 cli:
write: 45ms, compress: 8ms
write: 106ms, compress: 13ms
write: 33ms, compress: 10ms
write: 11ms, compress: 12ms
write: 11ms, compress: 40ms
write: 121ms, compress: 13ms
write: 14ms, compress: 20ms
write: 13ms, compress: 22ms
write: 19ms, compress: 10ms
write: 10ms, compress: 10ms
write: 112ms, compress: 28ms

Bug: 253568736
Test: presubmit
Change-Id: I09825df7196edf19c67ce936302643d7ca7f1aa9