Moved SafeWaitHandle and cancellationToken to shared (#18662)

* Moving SafeWaitHandle to shared

* Moved CancellationToken to shared

* _ remove from variable names

* Default change to Default(Token) and minor changes

* Fixing coreclr unix build

* moving semaphoreSlim to shared

* splitting safeWaitHandle to .windows and .unix

2 files changed, 32 insertions, 0 deletions

diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs
new file mode 100644
index 0000000000..66f17f0af7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.Windows.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.Win32.SafeHandles
+{
+    public sealed partial class SafeWaitHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        protected override bool ReleaseHandle() => Interop.Kernel32.CloseHandle(handle);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
new file mode 100644
index 0000000000..edb0cdfcaf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    public sealed partial class SafeWaitHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        // Called by P/Invoke marshaler
+        private SafeWaitHandle() : base(true)
+        {
+        }
+
+        public SafeWaitHandle(IntPtr existingHandle, bool ownsHandle) : base(ownsHandle)
+        {
+            SetHandle(existingHandle);
+        }
+    }
+}