Daniel D'Addario Chief TV CriticSPOILER ALERT: Do not read if you have not watched Episodes 8 and 9 of “Stranger Things 4,” now streaming on Netflix.Writing about the first seven episodes of the current, fourth season of “Stranger Things,” I noted that its ambition was both laudable and detrimental, gesturing back to a more exciting era of Netflix while also freighting each episode with more than it could bear.The final two episodes of the fourth season, which launched July 1, prove that doubly true. The moments that sing — including, once again, in the cadences of Kate Bush, this season’s musical patron sorceress — really are on a different level than just about anything the streamer has done lately.