tests: Split ZFS ZSTD test into new file

Split ZFS ZSTD test into its own test script. Add a check to the new
test script to see if the zfs utility installed on the host supports
"zstd" compression before running the test and fail the test if not. It
seems at least some zfs-fuse binaries do not support zstd compression
and the current test will fail in that case. Splitting into a new file
will avoid masking other test failures due to missing zstd support.

Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Glenn Washburn <development@efficientek.com>

Makefile.util.def

@@ -914,6 +914,12 @@ script = {
   common = tests/zfs_test.in;
 };
 
+script = {
+  testcase = native;
+  name = zfs_zstd_test;
+  common = tests/zfs_zstd_test.in;
+};
+
 script = {
   testcase = native;
   name = cpio_test;