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/Collections/Contracts/IUnsafeCollection.cs

@@ -0,0 +1,38 @@
+namespace Misaki.HighPerformance.LowLevel.Collections.Contracts;
+
+public unsafe interface IUnsafeCollection<T> : IEnumerable<T>, IDisposable
+    where T : unmanaged
+{
+    /// <summary>
+    /// Gets the number of elements in a collection. The value is read-only.
+    /// </summary>
+    public int Count
+    {
+        get;
+    }
+
+    /// <summary>
+    /// Indicates whether the object has been created. Returns true if the object is created, otherwise false.
+    /// </summary>
+    public bool IsCreated
+    {
+        get;
+    }
+
+    /// <summary>
+    /// Removes all elements from the collection. The collection will be empty after this operation.
+    /// </summary>
+    public void Clear();
+
+    /// <summary>
+    /// Changes the size of a collection or array to the specified value.
+    /// </summary>
+    /// <param name="newSize">Specifies the new size to which the collection or array should be adjusted.</param>
+    public void Resize(int newSize);
+
+    /// <summary>
+    /// Returns a pointer to an unmanaged memory location. This pointer can be used for low-level memory operations.
+    /// </summary>
+    /// <returns>The method returns a void pointer to the unsafe memory location.</returns>
+    public void* GetUnsafePtr();
+}