Include unrealized gains in backtesting result

[MDUYN]

Discussed in #280

^{Originally posted by amustapha December 24, 2024}
After running backtesting on a strategy, we get results that look like the screenshot above with orders that haven't been closed showing a net profit of 0. It might be quite helpful to show the floating (unrealized) profit or loss at the time when the backtesting finished.