They’re no longer paddling against the stream. There was a time when major studios’ pre-album marketing and teaser singles made it happen for budding hip-hop stars. No longer: They’re blasting out tracks on Spotify, Apple Music or other services and waiting for recognition to stream in. Playlists such as Spotify’s kingmaking RapCaviar — curated by just one man — have boosted music revenue growth into double digits for the first time since the late 1990s. And those receipts zoomed 69 percent to $3.9 billion last year, suggesting the Napster-battered industry’s finally healing.