“ Thor ” star Tessa Thompson charmed a packed audience at a BFI London Film Festival screen talk on Monday, reflecting on her varied career from Marvel blockbusters to intimate indie dramas, including her latest project “Hedda,” which premiered at the festival. The actor was particularly effusive about her “Thor” experience, describing director Taika Waititi as “a huge infant, just, he’s like an infant with a bank account.” Thompson praised Waititi’s childlike approach to filmmaking, noting “it’