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

This reverts commit 088924af2ad125f9135452223cdb8ecb90d9fb5a.

Bug: 168907513
Test: verified correct function of the cgroup v2 hierarchy in normal and
recovery mode

Change-Id: I6e9d21ebe832326ed5a5b2c356fe8363c1546a80
3 files changed