While Elina Svitolina prepares for Thursday’s semi-final against Czech No 7 Marketa Vondrousova, her friend Sergiy Stakhovsky has a very different path ahead of him, leading to the trenches on the road to Mariupol. At 37, Stakhovsky is nine years older than Svitolina, but he was Ukraine’s top-ranked player in his early twenties. “Hopefully it will be happy Monday after …