Add image processing and memory management features

Added new namespace `Misaki.HighPerformance.Image` for image processing, including classes for animated GIF handling and memory management.
Added `AnimatedFrameResult` class for individual frames in animated images.
Added `AnimatedGifEnumerator` class for enumerating frames in animated GIFs.
Added `ColorComponents` enum for different color formats.
Added `ImageInfo` struct for image dimensions and color components.
Added `CRuntime` class for low-level memory management functions.
Added `MemoryStats` class to track memory allocation statistics.
Added utility functions for creating multi-dimensional arrays.
Added new structures for fixed-size UTF-8 encoded strings.
Added benchmarking classes to test new memory management features.

Changed `StbImage.cs` to include new namespaces and functionality for image data manipulation.
Changed project files to target .NET 9.0 and enable new features.
Changed `Arena.cs` and `DynamicArena.cs` to use `nuint` for size parameters.
Changed `BitSet.cs` to enhance bit manipulation methods.
Changed `Program.cs` to run `FunctionPtrBenchmark` for performance testing.

Removed memory tracking code from `AllocationManager.cs`, including the `_allocated` dictionary and related logic.
Removed `Free` method from `IAllocator.cs` interface.
Removed `UNSAFE_COLLECTION_CHECK` preprocessor directive from the codebase.

Refactored various files to improve organization, moving from `Unsafe` to `LowLevel` namespace.
Refactored `MemoryUtilities` class to include new memory operation methods.
Refactored `UnsafeUtilities.cs` to support new collection structures.

Misaki.HighPerformance.LowLevel/Helpers/UnsafeUtilities.cs

@@ -0,0 +1,97 @@
+using Misaki.HighPerformance.LowLevel.Collections;
+using System.Runtime.CompilerServices;
+
+namespace Misaki.HighPerformance.LowLevel.Helpers;
+
+public static unsafe class UnsafeUtilities
+{
+    /// <summary>
+    /// Converts a pointer to a reference of a specified type.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of the reference to be created from the pointer.</typeparam>
+    /// <param name="ptr">Represents the memory address to be converted into a reference.</param>
+    /// <returns>Returns a reference of the specified type pointing to the given memory address.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static ref T AsRef<T>(void* ptr)
+    {
+        return ref SystemUnsfae.AsRef<T>(ptr);
+    }
+
+    /// <summary>
+    /// Returns the address of a specified variable in memory.
+    /// </summary>
+    /// <typeparam name="T">Represents the type of the variable whose address is being retrieved.</typeparam>
+    /// <param name="value">The variable whose memory address is to be obtained.</param>
+    /// <returns>A pointer to the memory address of the specified variable.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void* AddressOf<T>(ref T value)
+    {
+        return SystemUnsfae.AsPointer(ref value);
+    }
+
+    /// <summary>
+    /// Reads an element from an unmanaged array at a specified index using a pointer.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of elements in the unmanaged array.</typeparam>
+    /// <param name="ptr">Points to the start of the unmanaged array from which the element is read.</param>
+    /// <param name="index">Indicates the position of the element to be accessed within the array.</param>
+    /// <returns>Returns a pointer to the element located at the specified index.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static T* ReadArrayElementUnsafe<T>(void* ptr, int index) where T : unmanaged
+    {
+        return (T*)((byte*)ptr + index * sizeof(T));
+    }
+
+    /// <summary>
+    /// Reads an element from an unmanaged array using a pointer and index, returning a reference to the element.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of the elements in the unmanaged array.</typeparam>
+    /// <param name="ptr">Points to the start of the unmanaged array from which the element is read.</param>
+    /// <param name="index">Indicates the position of the element to be accessed in the array.</param>
+    /// <returns>A reference to the specified element in the unmanaged array.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static ref T ReadArrayElementRef<T>(void* ptr, int index) where T : unmanaged
+    {
+        return ref AsRef<T>(ReadArrayElementUnsafe<T>(ptr, index));
+    }
+
+    /// <summary>
+    /// Reads an element from an array at a specified index using a pointer to the array.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of the elements in the array, which must be unmanaged.</typeparam>
+    /// <param name="ptr">Points to the start of the array from which an element will be read.</param>
+    /// <param name="index">Indicates the position of the element to be accessed within the array.</param>
+    /// <returns>The element located at the specified index in the array.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static T ReadArrayElement<T>(void* ptr, int index) where T : unmanaged
+    {
+        return *ReadArrayElementUnsafe<T>(ptr, index);
+    }
+
+    /// <summary>
+    /// Writes a value to a specified index of an unmanaged array using a pointer.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of the value being written to the array, which must be an unmanaged type.</typeparam>
+    /// <param name="ptr">Points to the beginning of the unmanaged array where the value will be written.</param>
+    /// <param name="index">Indicates the position in the array where the value should be stored.</param>
+    /// <param name="value">Represents the value to be written to the specified index of the array.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void WriteArrayElement<T>(void* ptr, int index, T value) where T : unmanaged
+    {
+        *ReadArrayElementUnsafe<T>(ptr, index) = value;
+    }
+
+    /// <summary>
+    /// Converts an UnsafeArray of one unmanaged type to another unmanaged type without copying the elements.
+    /// </summary>
+    /// <typeparam name="TIn">Represents the type of elements in the input array.</typeparam>
+    /// <typeparam name="TOut">Represents the type of elements in the output array.</typeparam>
+    /// <param name="array">The input array containing elements of the specified input type.</param>
+    /// <returns>An UnsafeArray containing elements of the specified output type.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static UnsafeArray<TOut> CastArray<TIn, TOut>(UnsafeArray<TIn> array)
+        where TIn : unmanaged where TOut : unmanaged
+    {
+        return new UnsafeArray<TOut>(array.GetUnsafePtr(), array.Count * sizeof(TIn) / sizeof(TOut));
+    }
+}