Chris Willman Music WriterWhen Katy Perry sings that it’s “Never Really Over” at the top of her “Smile” album — a year-old introduction to a brand new collection — you can hear it as an expression of romantic regret, as intended, or take that title for what it really means for Perry: a vow of career imperishability. By just about anybody’s standards, she’s been on a cool streak, with seven years having transpired since the last No.