Introduce VirtualStack allocator, refactor memory management to use virtual memory stacks, and update documentation.
Added VirtualStack as a new stack allocator using virtual memory, replaced Stack with VirtualStack in allocation manager and related APIs, and updated TempJobAllocator to use VirtualArena. Introduced AllocationManagerInitOpts for allocator configuration. Replaced ENABLE_COLLECTION_CHECKS with ENABLE_SAFETY_CHECKS for safety checks. Removed Result.cs and updated project files and examples. Added comprehensive README files for all major packages and improved root documentation.
BREAKING CHANGE: Stack allocator replaced by VirtualStack; TempJobAllocator and AllocationManager initialization signatures changed; Result types removed.
Refactored Arena, DynamicArena, FreeList, and Stack to implement the new IMemoryAllocator<TSelf, TOpts> interface, standardizing allocation and free methods. Introduced MemoryPool<T, TOpts> for allocator lifetime management and AllocationHandle access. Updated Program.cs to use MemoryPool, replacing AllocationManager. Minor project file updates included.
