By Yew Lun Tian and Ryan Woo BEIJING (Reuters) -Chinese President Xi Jinping called for accelerating the building of a world-class military while touting the fight against COVID-19 as he kicked off a Communist Party Congress by focussing on security and reiterating policy priorities. Xi, 69, is widely expected to win a third leadership term at the conclusion of the week-long congress that began on Sunday morning, cementing his place as China’s most powerful ruler since Mao Zedong. Roughly 2,300 delegates from around the country gathered in the vast Great Hall of the People on the west side of …