Cache only unit paths in the pathfinder.

The path caching works on the assumption that the time saved from reusing a cached path outweights the cost of caching it in the first place.

For unit paths, this assumption holds. For path searchs, we spend more time caching them then we save when we get to reuse these cached paths. This is because they are reused less often, and calculating their key is more expensive in comparison.

OpenRA.Mods.Common/Traits/World/PathFinder.cs

@@ -22,7 +22,7 @@ namespace OpenRA.Mods.Common.Traits
 	{
 		public object Create(ActorInitializer init)
 		{
-			return new PathFinderCacheDecorator(new PathFinder(init.World), new PathCacheStorage(init.World));
+			return new PathFinderUnitPathCacheDecorator(new PathFinder(init.World), new PathCacheStorage(init.World));
 		}
 	}