The iconic cubes on the back wall and ceiling of Orchestra Hall are getting a shot of high-tech video and lighting design, with BAFTA-winning Tal Rosner using them as his canvas. For the Minnesota Orchestra’s season opener, the London-based designer is creating a visual landscape to accompany the orchestra’s performance of Igor Stravinsky’s “The Firebird,” part of the orchestra’s new multi-year series, “Sound Unbound,” developed around collabor…