Top diplomats based in Hong Kong received a special appeal from city leader Carrie Lam Cheng Yuet-ngor to join the recently concluded free mass testing scheme for Covid-19, the Post has learned, in a move seen as wanting to ensure full support for Beijing.The invitation to the consuls general was another testament to the administration’s all-out effort to ensure the success of the central government-backed programme which cost taxpayers HK$530 million (US$67.9 million).The chief executive…