Add SequenceEqual extension to prevent linq usage

this speeds up the state history integrity check by about an order of magnitude

src/BizHawk.Bizware.Graphics/BitmapBuffer.cs

@@ -8,6 +8,8 @@
 using System.IO;
 using System.Runtime.InteropServices;
 
+using BizHawk.Common.CollectionExtensions;
+
 using SDGraphics = System.Drawing.Graphics;
 
 namespace BizHawk.Bizware.Graphics
@@ -34,10 +36,6 @@ public unsafe class BitmapBuffer : IDisposable
 		private GCHandle CurrLockHandle;
 		private BitmapData CurrLock;
 
-		/// <summary>same as <see cref="Pixels"/> (<see cref="PixelFormat.Format32bppArgb">A8R8G8B8</see>)</summary>
-		public Span<int> AsSpan()
-			=> Pixels;
-
 		/// <exception cref="InvalidOperationException">already locked</exception>
 		/// <remarks>TODO add read/write semantic, for wraps</remarks>
 		public BitmapData LockBits()
@@ -545,7 +543,7 @@ private static int NextHigher(int k)
 		}
 
 		public bool SequenceEqual(BitmapBuffer other)
-			=> Width == other.Width && Height == other.Height && AsSpan().SequenceEqual(other.AsSpan());
+			=> Width == other.Width && Height == other.Height && Pixels.SequenceEqual(other.Pixels);
 
 		/// <summary>
 		/// Dumps this BitmapBuffer to a new System.Drawing.Bitmap
@@ -607,4 +605,4 @@ public void ToSysdrawingBitmap(Bitmap bmp)
 
 	}
 
-}
+}

src/BizHawk.Common/Extensions/CollectionExtensions.cs

@@ -321,5 +321,7 @@ public static bool IsSortedDesc<T>(this ReadOnlySpan<T> span)
 			for (int i = 0, e = span.Length - 1; i < e; i++) if (span[i + 1].CompareTo(span[i]) > 0) return false;
 			return true;
 		}
+
+		public static bool SequenceEqual<T>(this T[] a, ReadOnlySpan<T> b) where T : IEquatable<T> => a.AsSpan().SequenceEqual(b);
 	}
 }