[host/common] windows: provide delayExecution via nsleep

This change moves this platform specific sleep to `common` as the OS
agnostic `nsleep` function.

Ref PR #661

host/platform/Windows/include/windows/delay.h

@@ -1,26 +0,0 @@
-/**
- * Looking Glass
- * Copyright (C) 2017-2021 The Looking Glass Authors
- * https://looking-glass.io
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the Free
- * Software Foundation; either version 2 of the License, or (at your option)
- * any later version.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc., 59
- * Temple Place, Suite 330, Boston, MA 02111-1307 USA
- */
-
-#include <windows.h>
-
-void delayInit(void);
-
-// like sleep but more accurate
-void delayExecution(float ms);