Support ZSTD in userspace COW

Perf:
Lz4:
Update took 429 seconds
merge time 35.4s
cow size: 3.18GB

ZSTD:
Update took 676 seconds
merge time 49.4s
cow size: 2.62GB

Gz:
Update took 1057 seconds
merge time: 50.0s
cow size: 2.55GB

In summary, ZSTD is a middle point between LZ4 and GZ.

Speed: LZ4 > ZSTD > GZ
Space: LZ4 > ZSTD > GZ

Bug: 274129758

Change-Id: I203bf088b7c2a9ce429f75478799da0e7126febf