By Max Hunder and Mari Saito KYIV/KHARKIV, Ukraine (Reuters) -Ukrainian forces endured heavy artillery barrages on Sunday as they held off Russian attempts to capture Sievierodonetsk, the largest city Ukraine still controls in the eastern region of Luhansk, officials said. Russian shelling has destroyed all of Sievierodonetsk’s critical infrastructure, President Volodymyr Zelenskiy said, adding that Moscow’s main aim right now was to take the city. “Some 90% of buildings are damaged. More than two-thirds of the city’s housing stock has been completely destroyed. There is no telecommunication. …