By ELENA BECATOROS, OLEKSANDR STASHEVSKYI and RICARDO MAZALAN, Associated Press KYIV, Ukraine (AP) — A captured Russian soldier who pleaded guilty to killing a civilian was sentenced by a Ukrainian court Monday to life in prison — the maximum — amid signs the Kremlin may, in turn, put on trial some of the fighters who surrendered at Mariupol’s steelworks. Meanwhile, in a rare public expression of opposition