Optimize ZwinderStateManger.GetStateClosestToFrame

AllStates() sorted the returned states, but this order was not used anywhere else, so I've removed it. GetStateClosestToFrame is solvable in O(n), so sorting is not required there either.

This is an O(n log(n)) -> O(n) improvement that is mostly relevant for the state history integrity checker

src/BizHawk.Client.Common/movie/tasproj/ZwinderStateManager.cs

@@ -251,14 +251,13 @@ private IEnumerable<StateInfo> ReservedStates()
 		}
 
 		/// <summary>
-		/// Enumerate all states in reverse order
+		/// Enumerate all states in the following order: current -> recent -> gap -> reserved states
 		/// </summary>
 		internal IEnumerable<StateInfo> AllStates()
 		{
 			return CurrentAndRecentStates()
 				.Concat(GapStates())
-				.Concat(ReservedStates())
-				.OrderByDescending(s => s.Frame);
+				.Concat(ReservedStates());
 		}
 
 		public int Last => StateCache.Max();
@@ -474,8 +473,15 @@ public KeyValuePair<int, Stream> GetStateClosestToFrame(int frame)
 			if (frame < 0)
 				throw new ArgumentOutOfRangeException(nameof(frame));
 
-			var si = AllStates().First(s => s.Frame <= frame);
-			return new KeyValuePair<int, Stream>(si.Frame, si.Read());
+			StateInfo closestState = null;
+			foreach (var state in AllStates())
+			{
+				if (state.Frame <= frame && (closestState is null || state.Frame > closestState.Frame))
+				{
+					closestState = state;
+				}
+			}
+			return new KeyValuePair<int, Stream>(closestState!.Frame, closestState.Read());
 		}
 
 		public bool HasState(int frame)