<p>Jack Antonoff, the producer, finally got a night off on Friday. As his band Bleachers kicked off a new tour at Salt Shed, for once the focus turned away from the nonstop work he’s done for other artists to his main gig: the indie pop project he founded in 2013, before he was building up his cache of pop star cohorts.</p><p>OK, yes, Antonoff did just drop the new Taylor Swift “Toy Story 5” song, “I Knew It, I Knew You,” the same day and managed to slip in an acoustic cover of Lana Del Rey’s “M