When the “20 Years of Hottest 100” was announced yesterday, you’d be forgiven for experiencing some déjà vu. Didn’t we just celebrate the 20th anniversary of the Hottest 100 back in 2009, with another “All-Time Hottest 100?” Of course, this is supposed to commemorate the first annual Hottest 100 (songs from that year), and, conveniently,…