Enhance memory management and performance benchmarks

Added a new configuration setting in `.editorconfig` to sort system directives last and increased the maximum line length to 400 characters.
Added a new static class `MathUtilities` in `MathUtilities.cs` with a method `CeilPow2` for computing powers of two.
Added a new benchmark class `CollectionBenchmark` in `CollectionBenchmark.cs` to measure performance of standard versus unsafe arrays.
Added a new benchmark class `HashCodeBenchmark` in `HashCodeBenchmark.cs` to evaluate hash code generation performance.
Added new utility methods in `UnsafeUtilities.cs` for memory allocation and deallocation, including `Malloc`, `AlignedAlloc`, `Realloc`, and `Free`.
Added a new `AllocationType` enum in `AllocationType.cs` to specify memory allocation types.

Changed the project file `Misaki.HighPerformance.Mathematics.csproj` to target .NET 9.0 and enable implicit usings and nullable reference types.
Changed the `ParallelNoiseBenchmark` class in `ParallelNoiseBenchmark.cs` to improve memory allocation strategies and performance.
Changed memory management in `Arena.cs` and `DynamicArena.cs` to use custom `Malloc` and `Free` functions.
Changed the `IUnsafeCollection` interface in `IUnsafeCollection.cs` to include new methods for resizing collections and obtaining unsafe pointers.
Changed the `UnsafeArray.cs` to improve management of unsafe arrays, including constructor and method updates.
Changed the `UnsafeHashMap` and `UnsafeHashSet` classes to enhance performance and memory management.
Changed the `UnsafeCollectionExtensions` class to provide additional methods for copying elements and converting collections.
Changed the `ObjectPool` class in `ObjectPool.cs` to simplify cleanup and remove auto-cleanup functionality.
Changed job scheduling and worker classes in `JobExtensions.cs` and `JobWorker.cs` to improve job scheduling in a thread pool.

Removed commented-out code in `Program.cs` related to previous testing methods.
Removed auto-cleanup functionality from the `ObjectPool` class.

Misaki.HighPerformance.Unsafe/Collections/UnsafeHashSet.cs

@@ -0,0 +1,122 @@
+using Misaki.HighPerformance.Unsafe.Collections.Contracts;
+using Misaki.HighPerformance.Unsafe.Helpers;
+using System.Collections;
+using System.Runtime.CompilerServices;
+
+namespace Misaki.HighPerformance.Unsafe.Collections;
+
+/// <summary>
+/// A collection that provides fast, unsafe operations for managing a set of unmanaged types. It supports adding,
+/// removing, and checking for values.
+/// </summary>
+/// <typeparam name="T">Represents an unmanaged type that can be compared for equality.</typeparam>
+public unsafe struct UnsafeHashSet<T> : IUnsafeCollection<T>, IEnumerable<T>
+    where T : unmanaged, IEquatable<T>
+{
+    private struct Enumerator : IEnumerator<T>
+    {
+        internal HashMapHelper<T>.Enumerator _enumerator;
+
+        public Enumerator(HashMapHelper<T>* hashMap)
+        {
+            _enumerator = new HashMapHelper<T>.Enumerator(hashMap);
+        }
+
+        public T Current
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => _enumerator.buffer->_keys[_enumerator.index];
+        }
+
+        object IEnumerator.Current => Current;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool MoveNext() => _enumerator.MoveNext();
+
+        public void Reset() => _enumerator.Reset();
+
+        public readonly void Dispose()
+        {
+        }
+    }
+
+    private HashMapHelper<T> _hashMap;
+
+    public readonly int Count => _hashMap.Count;
+    public readonly int Capacity => _hashMap.Capacity;
+    public readonly bool IsCreated => _hashMap.IsCreated;
+
+    public IEnumerator<T> GetEnumerator() => new Enumerator((HashMapHelper<T>*)UnsafeUtilities.AddressOf(ref _hashMap));
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    public UnsafeHashSet(int capacity)
+    {
+        _hashMap = new HashMapHelper<T>(capacity, 0, HashMapHelper<T>.MINIMAL_CAPACITY);
+    }
+
+    /// <summary>
+    /// Adds a new value (unless it is already present).
+    /// </summary>
+    /// <param name="item">The value to add.</param>
+    /// <returns>True if the value was not already present.</returns>
+    public bool Add(T item)
+    {
+        return -1 != _hashMap.TryAdd(item);
+    }
+
+    /// <summary>
+    /// Removes a particular value.
+    /// </summary>
+    /// <param name="item">The value to remove.</param>
+    /// <returns>True if the value was present.</returns>
+    public bool Remove(T item)
+    {
+        return -1 != _hashMap.TryRemove(item);
+    }
+
+    /// <summary>
+    /// Returns true if a particular value is present.
+    /// </summary>
+    /// <param name="item">The value to check for.</param>
+    /// <returns>True if the value was present.</returns>
+    public bool Contains(T item)
+    {
+        return -1 != _hashMap.Find(item);
+    }
+
+    /// <summary>
+    /// Sets the capacity to match what it would be if it had been originally initialized with all its entries.
+    /// </summary>
+    public void TrimExcess() => _hashMap.TrimExcess();
+
+    /// <summary>
+    /// Returns an array with a copy of this set's values (in no particular order).
+    /// </summary>
+    /// <param name="allocator">The allocator to use.</param>
+    /// <returns>An array with a copy of the set's values.</returns>
+    public UnsafeArray<T> ToNativeArray(Allocator allocator)
+    {
+        return _hashMap.GetKeyArray(allocator);
+    }
+
+    public void Resize(int newSize)
+    {
+        _hashMap.Resize(newSize);
+    }
+
+    public void Clear()
+    {
+        _hashMap.Clear();
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public readonly void* GetUnsafePtr()
+    {
+        return _hashMap.Buffer;
+    }
+
+    public void Dispose()
+    {
+        _hashMap.Dispose();
+    }
+}