By Valentyn Ogirenko and Aziz El Yaakoubi KYIV/RIYADH (Reuters) – President Volodymyr Zelenskiy hailed as “superheroes” the senior Ukrainian commanders, including those who led the dogged defence of Mariupol, who were freed by Russia as part of a prisoner swap involving almost 300 people, including foreigners. Under the terms of the deal, which Turkey helped broker, 215 Ukrainians – most captured after the fall of the port city – were released on Wednesday. In exchange, Ukraine sent back 55 Russians and pro-Moscow Ukrainians. Ten foreigners were also freed following mediation by Saudi Crown Pr…