add refs

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

@@ -40,6 +40,7 @@ public static partial class ThreadPool
         [System.CLSCompliantAttribute(false)]
         public static unsafe 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.Collections.Generic.List<System.Threading.IThreadPoolWorkItem> callBacks, bool preferLocal) { throw null; }
         public static bool UnsafeQueueUserWorkItem(System.Threading.WaitCallback callBack, object? state) { throw null; }
         public static bool UnsafeQueueUserWorkItem<TState>(System.Action<TState> callBack, TState state, bool preferLocal) { throw null; }
         public static System.Threading.RegisteredWaitHandle UnsafeRegisterWaitForSingleObject(System.Threading.WaitHandle waitObject, System.Threading.WaitOrTimerCallback callBack, object? state, int millisecondsTimeOutInterval, bool executeOnlyOnce) { throw null; }

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

@@ -10,5 +10,6 @@
   <ItemGroup>
     <ProjectReference Include="..\..\System.Runtime\ref\System.Runtime.csproj" />
     <ProjectReference Include="..\..\System.Threading.Overlapped\ref\System.Threading.Overlapped.csproj" />
+    <ProjectReference Include="..\..\System.Collections\ref\System.Collections.csproj" />
   </ItemGroup>
 </Project>