Sped up FindShortestPath alg

When finding shortest path, we no longer check intermediary tiles for the next step, since they will always have a longer path than the edge tiles (since from there, we need to pass through an edge tile anyway)

core/src/com/unciv/logic/map/UnitMovementAlgorithms.kt

@@ -81,9 +81,9 @@ class UnitMovementAlgorithms(val tileMap: TileMap){
 
            if(newTilesToCheck.isEmpty()) return emptyList() // there is NO PATH (eg blocked by enemy units)
 
-           tilesToCheck = newTilesToCheck
+           tilesToCheck = newTilesToCheck.filterNot {tile -> tile.neighbors.all{newTilesToCheck.contains(it) || tilesToCheck.contains(it) } }
            distance++
        }
    }
 
-}
+}