Add a second mode for statistics based on trading position.

Currently, the calculations in the statistics section (e.g., profit and loss) are based on the logic that the first open trade corresponds to the first closed trade (FIFO). However, this approach doesn’t always align with a trader’s needs. For instance, my strategy involves gradually building a position in an asset and closing it when the price exceeds the average entry point. In this case, a good position close results in no losses. However, under the current implementation, losses are accumulated in the statistics if I close below the initial entry point.

I propose introducing an additional alternative calculation mode in the statistics section, based on cumulative positions rather than individual trades.