Implement WieldMeshSceneNode which improves wield mesh rendering

- Don't create and cache an extruded mesh for every (non-node) item.
  Instead use a single one per image resolution.

- For cubic nodes reuse a single wield mesh too

- Improve lighting of the wielded item

- Increase far value of wield mesh scene camera, fixes #1770

- Also includes some minor refactorings of Camera and GenericCAO.

src/game.cpp

@@ -3656,7 +3656,7 @@ void Game::updateFrame(std::vector<aabb3f> &highlight_boxes,
 
 		if (mlist && (client->getPlayerItem() < mlist->getSize())) {
 			ItemStack item = mlist->getItem(client->getPlayerItem());
-			camera->wield(item, client->getPlayerItem());
+			camera->wield(item);
 		}
 		runData->update_wielded_item_trigger = false;
 	}