generic: test zero range crossing isize within single block

generic: test zero range crossing isize within single block

Exercise the situation that cause ext4 to BUG_ON() when we use
zero range to zero a range which starts within the isize but ends
past the isize but still in the same block. This particular problem
has only been seen on systems with page_size > block_size.

This tests exercises the problem fixed in kernel with commit
0f2af21aae11972fa924374ddcf52e88347cf5a8
ext4: Allocate entire range in zero range

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>