Revert^4 "libprocessgroup: uid/pid hierarchy for cgroup v2" am: 4dac81680f am: b33b95f6ef

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1585101

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ie1d384f639af0996b4b23c51b5e41650b8c0ff57