Add unbounded task scheduler for divisor testing

PerfectNumbers.Core/MersenneNumberDivisorByDivisorTester.cs

@@ -253,7 +253,8 @@ public static class MersenneNumberDivisorByDivisorTester
 		{
 			ParallelOptions options = new()
 			{
-				MaxDegreeOfParallelism = workerCount
+				MaxDegreeOfParallelism = workerCount,
+				TaskScheduler = UnboundedTaskScheduler.Instance
 			};
 
 			Parallel.ForEach(filteredPrimes, options, ProcessPrime);

PerfectNumbers.Core/UnboundedTaskScheduler.cs

@@ -0,0 +1,34 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace PerfectNumbers.Core;
+
+public sealed class UnboundedTaskScheduler : TaskScheduler
+{
+        public static UnboundedTaskScheduler Instance { get; } = new();
+
+        private UnboundedTaskScheduler()
+        {
+        }
+
+        public override int MaximumConcurrencyLevel => int.MaxValue;
+
+        protected override void QueueTask(Task task)
+        {
+                ThreadPool.UnsafeQueueUserWorkItem(static state =>
+                {
+                        (UnboundedTaskScheduler Scheduler, Task Task) tuple = ((UnboundedTaskScheduler, Task))state!;
+                        tuple.Scheduler.TryExecuteTask(tuple.Task);
+                }, (this, task));
+        }
+
+        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+        {
+                return TryExecuteTask(task);
+        }
+
+        protected override IEnumerable<Task>? GetScheduledTasks()
+        {
+                return null;
+        }
+}