Merge pull request #18401 from anitazha/oomdxattr

oomd: implement avoid/omit support for cgroups

diff --cc src/basic/cgroup-util.c
Simple merge

diff --cc src/basic/cgroup-util.h
Simple merge

diff --cc src/core/cgroup.h
Simple merge

diff --cc src/core/dbus-cgroup.c
Simple merge

diff --cc src/core/load-fragment.c
Simple merge

diff --cc src/oom/oomd-manager.c
Simple merge

diff --cc test/test-functions
Simple merge