Christian Tetzlaff, one of the world’s most admired and versatile violinists, is the National Symphony Orchestra’s guest artist this week for a performance of Beethoven’s Violin Concerto. For the past two decades, he and Maestro Christoph Eschenbach have worked together quite a few times, most recently on concertos by Lalo and Shostakovich, but this will be their first Beethoven concerto collaboration.