Nick Vivarelli International CorrespondentMilan’s venerable La Scala opera house on Monday will stage a globally distributed TV gala event featuring its mask-wearing orchestra in the empty venue and a multimedia medley of arias and other performances by opera, ballet, pop music and screen stars, substituting its canceled season opener.Due to the pandemic, La Scala has been forced to call off its traditional December opera opening, among the top events on Europe’s cultural calendar, for the