Block cloning tests.

The test mostly focus on testing various corner cases.
The tests take a long time to run, so for the common.run runfile
we randomly select a hundred tests.
To run all the bclone tests, bclone.run runfile should be used.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes #15631

tests/zfs-tests/include/commands.cfg

@@ -98,7 +98,8 @@ export SYSTEM_FILES_COMMON='awk
     uname
     uniq
     vmstat
-    wc'
+    wc
+    xargs'
 
 export SYSTEM_FILES_FREEBSD='chflags
     compress

tests/zfs-tests/include/math.shlib

@@ -123,10 +123,21 @@ function verify_ne # <a> <b> <type>
 #
 # $1 lower bound
 # $2 upper bound
+# [$3 how many]
 function random_int_between
 {
 	typeset -i min=$1
 	typeset -i max=$2
+	typeset -i count
+	typeset -i i
 
-	echo $(( (RANDOM % (max - min + 1)) + min ))
+	if [[ -z "$3" ]]; then
+		count=1
+	else
+		count=$3
+	fi
+
+	for (( i = 0; i < $count; i++ )); do
+		echo $(( (RANDOM % (max - min + 1)) + min ))
+	done
 }