Remove all concurrency code

Muddled the code too much, and only gave a marginal performance improvement in the grand scheme of things. Other ways to parallelize MCTS will be nicer to implement and could yield better results.

Benchmark/Program.cs

@@ -46,22 +46,22 @@ internal static class Program
 
         var config = new SolverConfig()
         {
-            Iterations = 100_000,
+            Iterations = 30_000,
             ThreadCount = 8,
         };
 
         Debugger.Break();
         var s = Stopwatch.StartNew();
         if (true) {
-            (_, var state) = SolverUtils.SearchStepwise<SolverSingle>(config, input, a => Console.WriteLine(a));
+            (_, var state) = Solver.Crafty.Solver.SearchStepwise(config, input, a => Console.WriteLine(a));
             Console.WriteLine($"Qual: {state.Quality}/{state.Input.Recipe.MaxQuality}");
         }
         else
         {
-            (var actions, _) = SolverUtils.SearchOneshot<SolverConcurrent>(config, input);
-            foreach (var action in actions)
-                Console.Write($">{action.IntName()}");
-            Console.WriteLine();
+            //(var actions, _) = SolverUtils.SearchOneshot<SolverConcurrent>(config, input);
+            //foreach (var action in actions)
+            //    Console.Write($">{action.IntName()}");
+            //Console.WriteLine();
         }
         s.Stop();
         Console.WriteLine($"{s.Elapsed.TotalMilliseconds:0.00}");