selftests: cgroup: Add 'malloc' failures checks in test_memcontrol

selftests: cgroup: Add 'malloc' failures checks in test_memcontrol

[ Upstream commit c83f320e55a49abd90629f42a72897afd579e0de ]

There are several 'malloc' calls in test_memcontrol, which can be
unsuccessful. This patch will add 'malloc' failures checking to
give more details about test's fail reasons and avoid possible
undefined behavior during the future null dereference (like the
one in alloc_anon_50M_check_swap function).

Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>