By Yew Lun Tian and Ryan Woo BEIJING (Reuters) -President Xi Jinping on Sunday touted the ruling Communist Party’s fight against COVID-19 while reiterating support for the private sector and allowing markets to play a key role even as China fine-tunes a “socialist economic system”. During a speech at the start of a congress where he is widely expected to win a third leadership term that cements his place as the country’s most powerful ruler since Mao Zedong, Xi also lauded the party’s taking control of the situation in Hong Kong, which was rocked by anti-government protests in 2019. The twice-…