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.Mathematics/Utilities.ttinclude

@@ -0,0 +1,29 @@
+<#@ import namespace="System.Text" #>
+<#@ import namespace="System.Collections.Generic" #>
+<#@ import namespace="System.Linq" #>
+<#+
+public int[] dimensions = new[] { 2, 3, 4 };
+
+public IEnumerable<string> GenerateSwizzles(string[] pool, int maxLen)
+{
+    IEnumerable<string> Recurse(string prefix, int depth)
+    {
+        if (depth == 0)
+        {
+            yield return prefix;
+        }
+        else
+        {
+            foreach (var c in pool)
+            {
+                foreach (var s in Recurse(prefix + c, depth - 1))
+                {
+                    yield return s;
+                }
+            }
+        }
+    }
+
+    return Enumerable.Range(2, maxLen - 1).SelectMany(len => Recurse("", len));
+}
+#>