Merge branch 'Support storing struct cgroup * objects as kptrs'

David Vernet says:

====================

In [0], we added support for storing struct task_struct * objects as
kptrs. This patch set extends this effort to also include storing struct
cgroup * object as kptrs.

As with tasks, there are many possible use cases for storing cgroups in
maps. During tracing, for example, it could be useful to query cgroup
statistics such as PSI averages, or tracking which tasks are migrating
to and from the cgroup.

[0]: https://lore.kernel.org/all/20221120051004.3605026-1-void@manifault.com/
====================

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>