btrfs-progs: tests: Introduce fsck-tests/018-leaf-crossing-stripes

To test if fsck can check detec "leaf crossing stripes".

This function was introduced from patch titled:
btrfs-progs: fsck: Check if a metadata tree block crossing stripe boundary

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
[renamed and other minor changes]
Signed-off-by: David Sterba <dsterba@suse.com>

tests/fsck-tests/018-leaf-crossing-stripes/test.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+source $TOP/tests/common
+
+check_prereq btrfs
+
+image=$(extract_image "./default_case.raw.xz")
+run_check_stdout $TOP/btrfs check "$image" 2>&1 |
+	grep -q "crossing stripe boundary" ||
+	_fail "no expected error message in the output"
+
+rm -f "$image"