“Edinburgh is full of comedians who want to be TV presenters,” says veteran stand-up Scott Capurro with a sweet, sunny smile. “Why don’t you just cut yourself, you self-loathing cunts…?” August in Scotland. The world’s largest arts festival: 258 venues, over 2,500 shows, around 1.8 million tickets sold. Imagine 10 back-to-back Glastonburys spread across 25…