Refactor thread cache management in allocators

Refactored thread-local stack allocator in AllocationManager to use ThreadLocalStackPool, removing global stack pointer arrays and locks. In FreeList, replaced fixed-size cache array and maxConcurrencyLevel with a dynamic linked-list system using SharedState and CacheReclaimer for thread cache lifecycle management. Block headers now store cache pointers instead of indices. Updated allocation/free logic and tests accordingly. Bumped assembly version to 3.1.3.

Misaki.HighPerformance.LowLevel/Buffer/VirtualStack.cs

@@ -24,6 +24,7 @@ public unsafe struct VirtualStack : IMemoryAllocator<VirtualStack, VirtualStack.
         private readonly nuint _originalOffset;
 
         public readonly AllocationHandle AllocationHandle => _handle;
+        public readonly nuint OriginalOffset => _originalOffset;
 
         internal Scope(VirtualStack* allocator, AllocationHandle handle)
         {