Remove path caching.

The path cache was originally a moderate benefit, but over time a couple of things have conspired against it:

- Only paths with BlockedByActor.None are cached. Originally all paths regardless of blocking were cached but this was deemed unacceptable due to potentially returning outdated paths as actors move about. Paths with BlockedByActor.None are only invalidated if terrain conditions change, which are rarer.
- Move will try and find a path 4 times, trying with a different BlockedByActor check each time. BlockedByActor.None is the last check and only reached if the other searches fail. This is a rare scenario.

Overall, this means the hit rate for the cache is almost non-existent. Given the constraints on path validity it seems unlikely that the hit rate could be improved significantly, therefore it seems reasonable to remove the cache entirely to remove the overhead of cache management.

OpenRA.Game/CacheStorage.cs

@@ -1,20 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2021 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-namespace OpenRA
-{
-	public interface ICacheStorage<T>
-	{
-		void Remove(string key);
-		void Store(string key, T data);
-		T Retrieve(string key);
-	}
-}