cri/server: use containerd/oci instead of libcontainer/devices

Looks like we had our own copy of the "getDevices" code already, so use
that code (which also matches the code that's used to _generate_ the spec,
so a better match).

Moving the code to a separate file, I also noticed that the _unix and _linux
code was _exactly_ the same (baring some `//nolint:` comments), so also
removing the duplicated code.

With this patch applied, we removed the dependency on the libcontainer/devices
package (leaving only libcontainer/user).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/opencontainers/runc/libcontainer/devices/device_unix.go

@@ -1,16 +0,0 @@
-// +build !windows
-
-package devices
-
-import (
-	"errors"
-
-	"golang.org/x/sys/unix"
-)
-
-func (d *Rule) Mkdev() (uint64, error) {
-	if d.Major == Wildcard || d.Minor == Wildcard {
-		return 0, errors.New("cannot mkdev() device with wildcards")
-	}
-	return unix.Mkdev(uint32(d.Major), uint32(d.Minor)), nil
-}