“Bombshell” did arrive on Broadway this week to a rapturous reception at the 1,700-seat Minskoff Theatre — but only as a one-night charity event in which members of the original cast reunited to sing and dance their way through the songbook created by Scott Wittman and Marc Shaiman. Tickets to the Monday night show had sold out in about an hour in April after a Kickstarter campaign raised $300,000-plus to defer development expenses.