This pulls in sylabs PR

• deps: switch to runc/libcontainer/cgroups cgroup manager sylabs/singularity#531
  which fixed
• Migrate from containerd/cgroups to opencontainers/runc/libcontainer/cgroups sylabs/singularity#530

The original PR description was:

Switch our cgroups management dependency from containerd/cgroups to opencontainers/runc/libcontainer/cgroups in order to ease implementation of systemd / unprivileged delegation etc.

This is the first step of the process of tidying up the cgroups manager code. At this point I have chosen to:

• Implement the existing cgroups.Manager interface with a new cgroups.ManagerLC in manager_libcontainer_linux.go. This avoids code changes in the runtime for this initial swap-out.
• Remove the old containerd/cgroups based cgroups.ManagerV1 and cgroups.ManagerV2.
• Retain the tests that were run against the old ManagerV1 and ManagerV2 and point them to ManagerLC.

The purpose of this approach is to first be happy that there's no impact from switching the dep out.

Refactoring will occur to address the facts that:

• The cgroups.Manager is a pretty nasty interface... and involves a bunch of messy code in the manager to implement.
• We can work much more directly with the libcontainer code's New/Set/Apply cycle.
• We need to extend for systemd and rootless cgroups management.
• Testing needs to be overhauled and expanded for the above.