reposition tanks on map switch, rework map logic

tanks-backend/TanksServer/GameLogic/ChangeToRequestedMap.cs

@@ -0,0 +1,24 @@
+namespace TanksServer.GameLogic;
+
+internal sealed class ChangeToRequestedMap(
+    MapService mapService,
+    MapEntityManager entityManager,
+    EmptyTileFinder emptyTileFinder
+) : ITickStep
+{
+    private MapPrototype? _requestedMap;
+
+    public ValueTask TickAsync(TimeSpan delta)
+    {
+        var changeTo = Interlocked.Exchange(ref _requestedMap, null);
+        if (changeTo == null)
+            return ValueTask.CompletedTask;
+
+        mapService.SwitchTo(changeTo);
+        foreach (var t in entityManager.Tanks)
+            t.Position = emptyTileFinder.ChooseEmptyTile().GetCenter().ToFloatPosition();
+        return ValueTask.CompletedTask;
+    }
+
+    public void Request(MapPrototype map) => _requestedMap = map;
+}