Fix a couple missing SupportedOSPlatform attributes on ThreadPool (#55148)

Author: stephentoub

src/coreclr/System.Private.CoreLib/src/System/Threading/ThreadPool.CoreCLR.cs

@@ -450,6 +450,7 @@ internal static bool PerformRuntimeSpecificGateActivities(int cpuUtilization)
         private static extern unsafe bool PostQueuedCompletionStatus(NativeOverlapped* overlapped);
 
         [CLSCompliant(false)]
+        [SupportedOSPlatform("windows")]
         public static unsafe bool UnsafeQueueNativeOverlapped(NativeOverlapped* overlapped) =>
             PostQueuedCompletionStatus(overlapped);
 
@@ -547,6 +548,7 @@ RegisteredWaitHandle registeredWaitHandle
              );
 
         [Obsolete("ThreadPool.BindHandle(IntPtr) has been deprecated.  Please use ThreadPool.BindHandle(SafeHandle) instead.", false)]
+        [SupportedOSPlatform("windows")]
         public static bool BindHandle(IntPtr osHandle)
         {
             return BindIOCompletionCallbackNative(osHandle);

src/libraries/System.Threading.ThreadPool/ref/System.Threading.ThreadPool.cs

@@ -22,6 +22,7 @@ public static partial class ThreadPool
         public static long PendingWorkItemCount { get { throw null; } }
         public static int ThreadCount { get { throw null; } }
         [System.ObsoleteAttribute("ThreadPool.BindHandle(IntPtr) has been deprecated.  Please use ThreadPool.BindHandle(SafeHandle) instead.", false)]
+        [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static bool BindHandle(System.IntPtr osHandle) { throw null; }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static bool BindHandle(System.Runtime.InteropServices.SafeHandle osHandle) { throw null; }
@@ -43,6 +44,7 @@ public static partial class ThreadPool
         public static bool SetMaxThreads(int workerThreads, int completionPortThreads) { throw null; }
         public static bool SetMinThreads(int workerThreads, int completionPortThreads) { throw null; }
         [System.CLSCompliantAttribute(false)]
+        [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public unsafe static bool UnsafeQueueNativeOverlapped(System.Threading.NativeOverlapped* overlapped) { throw null; }
         public static bool UnsafeQueueUserWorkItem(System.Threading.IThreadPoolWorkItem callBack, bool preferLocal) { throw null; }
         public static bool UnsafeQueueUserWorkItem(System.Threading.WaitCallback callBack, object? state) { throw null; }

src/mono/System.Private.CoreLib/src/System/Threading/ThreadPool.Mono.cs

@@ -19,6 +19,7 @@ private static unsafe void NativeOverlappedCallback(object? obj)
         }
 
         [CLSCompliant(false)]
+        [SupportedOSPlatform("windows")]
         public static unsafe bool UnsafeQueueNativeOverlapped(NativeOverlapped* overlapped)
         {
             // OS doesn't signal handle, so do it here (CoreCLR does this assignment in ThreadPoolNative::CorPostQueuedCompletionStatus)
@@ -28,6 +29,7 @@ public static unsafe bool UnsafeQueueNativeOverlapped(NativeOverlapped* overlapp
         }
 
         [Obsolete("ThreadPool.BindHandle(IntPtr) has been deprecated.  Please use ThreadPool.BindHandle(SafeHandle) instead.", false)]
+        [SupportedOSPlatform("windows")]
         public static bool BindHandle(IntPtr osHandle)
         {
             throw new PlatformNotSupportedException(SR.Arg_PlatformNotSupported); // Replaced by ThreadPoolBoundHandle.BindHandle