Alan Cumming is having quite the year. When we caught up with him in April, he was taking a break from a tour of a musical he’d written called “The High Life,” which was based on a sitcom he wrote in the 1990s about “a crappy Scottish airline.” He was planning to do another month of that, followed by a film and a new musical at Pitlochry Festival Theatre, the performing-arts venue in the Scottish Highlands where he serves as artistic director. A…