OCI Modifiers for Windows

Signed-off-by: John Howard <jhoward@microsoft.com>

Needed for the containerd work on Windows and integrating the
oci package from containerd into moby.

No longer sets defaults for
 - .Process.ConsoleSize
 - .Windows.IgnoreFlushesDuringBoot
 - .Windows.Network.AllowUnqualifiedDNSQuery

Adds helper functions and tests for
 - WithWindowsIgnoreFlushesDuringBoot
 - WithWindowNetworksAllowUnqualifiedDNSQuery

Updates `ctr run` on Windows to use the new helper functions,
ConsoleSize is already handled.

oci/spec.go

@@ -247,17 +247,8 @@ func populateDefaultWindowsSpec(ctx context.Context, s *Spec, id string) error {
 		Root:    &specs.Root{},
 		Process: &specs.Process{
 			Cwd: `C:\`,
-			ConsoleSize: &specs.Box{
-				Width:  80,
-				Height: 20,
-			},
-		},
-		Windows: &specs.Windows{
-			IgnoreFlushesDuringBoot: true,
-			Network: &specs.WindowsNetwork{
-				AllowUnqualifiedDNSQuery: true,
-			},
 		},
+		Windows: &specs.Windows{},
 	}
 	return nil
 }