Uses a much nicer CPU tuning configuration, leveraging systemd's
AllowedCPUs and CPUAffinity options within a set of slices (some
default, some custom).
Configuration is also greatly simplified versus the previous
implementation, simply asking for a number of CPUS for both the system
and OSDs, and calculating everything else that is required.
Also switches (back) to the v2 unified cgroup hierarchy by default as
required by the systemd AllowedCPUs directive.
This is required on Debian 11 to use the cset tool, since the newer
systemd implementation of a unified cgroup hierarchy is not compatible
with the cset tool.
Ref for future use:
https://github.com/lpechacek/cpuset/issues/40
