add ENTITY_NONE, ENTITY_AUTO reserved entity id & update player.set_entity(...)

src/logic/scripting/lua/libs/libplayer.cpp

@@ -229,7 +229,9 @@ static int l_set_entity(lua::State* L) {
     if (player == nullptr) {
         return 0;
     }
-    if (auto entity = get_entity(L, 2)) {
+    if (lua::isnumber(L, 2)) {
+        player->setEntity(lua::tointeger(L, 2));
+    } else if (auto entity = get_entity(L, 2)) {
         player->setEntity(entity->getUID());
     }
     return 0;