TORONTO — Attention, Ontario: Resume breathing. That show you’ve been counting on to bring in tourists? It just might do the trick. The most expensive stage show ever (more than $23 million U.S.), the musical version of “The Lord of the Rings” began its world premiere engagement at the Princess of Wales Theatre right on schedule. Seven weeks ago, technical glitches made the first preview clock in at 5 hours. These days “LOTR” runs 3 hours and 50 minutes, with two intermissions and a song after the curtain call. It may not be the 3 hours, 30 minutes that producer Kevin Wallace envisioned, but it doesn’t feel overlong. [More]