Director George Sidney’s “Bathing Beauty” (1944) is a delirious movie musical. It is, in many respects, an exemplar of the genre, and while It’s not the best, it ain’t bad. Sidney’s picture is particularly head-snapping in that it includes a dazzling array of musical talents — all of whom had to be accounted for in one way or another. The film is less a narrative continuum than a catch-as-catch-can variety show.