feat(buffer): add TLSF allocator and seqlock primitives

Added a TLSF (Two-Level Segregated Fit) memory allocator with O(1) allocation, free, and reallocation in `TLSF.cs`, plus comprehensive unit tests. Introduced a cache-line-padded `SeqLock` synchronization primitive. Refactored vector extension code for conciseness and fixed its usage to `extension(ref ...)`. Updated namespaces, removed unused code, and improved assertion and diagnostics. Updated NuGet dependencies and project files.

Misaki.HighPerformance.LowLevel/Buffer/Stack.cs

@@ -1,5 +1,4 @@
 using Misaki.HighPerformance.LowLevel.Utilities;
-using System.Collections;
 using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Buffer;