add runc shim support for sched core

In linux 5.14 and hopefully some backports, core scheduling allows processes to
be co scheduled within the same domain on SMT enabled systems.

The containerd impl sets the core sched domain when launching a shim. This
allows a clean way for each shim(container/pod) to be in its own domain and any
additional containers, (v2 pods) be be launched with the same domain as well as
any exec'd process added to the container.

kernel docs: https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/core-scheduling.html

Signed-off-by: Michael Crosby <michael@thepasture.io>

cmd/containerd/command/main.go

@@ -184,6 +184,7 @@ can be used and modified as necessary as a custom configuration.`
 			s   *server.Server
 			err error
 		}
+
 		// run server initialization in a goroutine so we don't end up blocking important things like SIGTERM handling
 		// while the server is initializing.
 		// As an example opening the bolt database will block forever if another containerd is already running and containerd