HONG KONG—Hong Kong will test its entire population of 7.5 million people for COVID-19 in March, the city’s leader said Tuesday, as it grapples with its worst outbreak mainly caused by the Omicron variant. The population will be tested three times in March, Hong Kong Chief Executive Carrie Lam said. She said testing capacity will be boosted to 1 million a day or more. “Since we have a population of some 7 million people, testing will take about seven days,” she said. Hong Kong has reported about 5,000 new daily infections since Feb. 15, with the cases threatening to overwhelm its healthcare system. Since the current surge that began at the beginning of the year, the city has recorded nearly 54,000 cases and 145 deaths. The order for citywide testing comes after mainland Chinese authorities dispatched epidemiologists, health workers, and other medical resources last week to help contain the outbreak …