tools:cgroup:memcg_shrinker remove redundant import

Remove redundant import of the sys module.

Also use the sort function instead of sorted. It sorts the direct array
without create the new one in memory.

Link: https://lkml.kernel.org/r/20230108105023.4289-1-apantykhin@gmail.com
Signed-off-by: Alexander Pantyukhin <apantykhin@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools: add memcg_shrinker.py

Add a simple tool which prints a sorted list of shrinker lists in the
following format: (number of objects, shrinker name, cgroup).

Example:
$ ./memcg_shrinker.py -n 10
2090 sb-sysfs-26 /sys/fs/cgroup/system.slice
1809 sb-sysfs-26 /sys/fs/cgroup/system.slice/systemd-udevd.service
1044 sb-btrfs:vda2-24 /sys/fs/cgroup/system.slice/system-dbus\x2d:1.3\...
861 sb-btrfs:vda2-24 /sys/fs/cgroup/system.slice/system-dbus\x2d:1.3\...
804 sb-btrfs:vda2-24 /sys/fs/cgroup/system.slice
643 sb-btrfs:vda2-24 /sys/fs/cgroup/system.slice/firewalld.service
616 sb-cgroup2-30 /sys/fs/cgroup/init.scope
275 sb-sysfs-26 /
238 sb-proc-25 /sys/fs/cgroup/system.slice/systemd-journald.service
225 sb-proc-25 /sys/fs/cgroup/system.slice/abrtd.service

Link: https://lkml.kernel.org/r/20220601032227.4076670-6-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>