Remove dependency on tar2vhd for LCOW differ

This change no longer requires the use of a UtlityVM on Windows to convert the
layer tar to an ext4 vhd for LCOW. This has a significant performance boost
that makes linux/amd64 layer extraction comparable to native Linux performance.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/runhcs/vm.go

@@ -0,0 +1,43 @@
+package runhcs
+
+import (
+	"encoding/json"
+
+	"github.com/Microsoft/go-winio"
+)
+
+// VMRequestOp is an operation that can be issued to a VM shim.
+type VMRequestOp string
+
+const (
+	// OpCreateContainer is a create container request.
+	OpCreateContainer VMRequestOp = "create"
+	// OpSyncNamespace is a `cni.NamespaceTypeGuest` sync request with the UVM.
+	OpSyncNamespace VMRequestOp = "sync"
+	// OpUnmountContainer is a container unmount request.
+	OpUnmountContainer VMRequestOp = "unmount"
+	// OpUnmountContainerDiskOnly is a container unmount disk request.
+	OpUnmountContainerDiskOnly VMRequestOp = "unmount-disk"
+)
+
+// VMRequest is an operation request that is issued to a VM shim.
+type VMRequest struct {
+	ID string
+	Op VMRequestOp
+}
+
+// IssueVMRequest issues a request to a shim at the given pipe.
+func IssueVMRequest(pipepath string, req *VMRequest) error {
+	pipe, err := winio.DialPipe(pipepath, nil)
+	if err != nil {
+		return err
+	}
+	defer pipe.Close()
+	if err := json.NewEncoder(pipe).Encode(req); err != nil {
+		return err
+	}
+	if err := GetErrorFromPipe(pipe, nil); err != nil {
+		return err
+	}
+	return nil
+}