feat: Adds a single threaded array pool (#967)

## Added Feature
Adds a single threaded array pool that works exactly the same as `ArrayPool<T>.Shared`.
The `STArrayPool<T>.Shared` can only be used on a single thread, the main game thread of the server.

Note: Unlike the built-in array pool, there is no hook into the _GC Gen 2_. This means to relieve potentially high memory pressure, `ArrayPool<T>.Shared.Trim()` must be called. The pool will only release arrays _after two successive calls within 10 seconds or longer_. If the server is at less than 70% total memory usage, or the server is not going to use this pool for something egregious, then don't bother ever calling Trim().


## Changes
- [X] Fixes ArrayPool calls that should be cleared due to references.
- [X] Benchmarks against ArrayPool with 4+ rented arrays deep of the same length.
- [x] Unit tests

Projects/Benchmarks/Program.cs

@@ -26,7 +26,9 @@ namespace Benchmarks
             //var mapMobilesSelectors = BenchmarkRunner.Run<MapMobileSelectors>();
             //var mapMultiTilesSelectors = BenchmarkRunner.Run<MapMultiTilesSelectors>();
             //var mapMultiSelectors = BenchmarkRunner.Run<MapMultiSelectors>();
-            var mapItemsSelectors = BenchmarkRunner.Run<MapItemSelectors>();
+            // var mapItemsSelectors = BenchmarkRunner.Run<MapItemSelectors>();
+            // var stArray = BenchmarkRunner.Run<BenchmarkSTArray>();
+            var pooledRefQueue = BenchmarkRunner.Run<BenchmarkPooledRefQueue>();
         }
     }
 }