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
diff --git a/init/Android.bp b/init/Android.bp
index 7b52903..41c7a95 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -169,6 +169,7 @@
         "libfsverity_init",
         "liblmkd_utils",
         "liblz4",
+        "libzstd",
         "libmini_keyctl_static",
         "libmodprobe",
         "libprocinfo",
@@ -370,6 +371,7 @@
         "libprotobuf-cpp-lite",
         "libsnapshot_cow",
         "liblz4",
+        "libzstd",
         "libsnapshot_init",
         "update_metadata-protos",
         "libprocinfo",