Move client's options to separate files

This should help in discovering the available options for a given object.

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

spec.go

@@ -2,17 +2,6 @@ package containerd
 
 import specs "github.com/opencontainers/runtime-spec/specs-go"
 
-// SpecOpts sets spec specific information to a newly generated OCI spec
-type SpecOpts func(s *specs.Spec) error
-
-// WithProcessArgs replaces the args on the generated spec
-func WithProcessArgs(args ...string) SpecOpts {
-	return func(s *specs.Spec) error {
-		s.Process.Args = args
-		return nil
-	}
-}
-
 // GenerateSpec will generate a default spec from the provided image
 // for use as a containerd container
 func GenerateSpec(opts ...SpecOpts) (*specs.Spec, error) {