Rolling Stones’ “Scarlet” video Thursday on YouTube was preceded by a chat between its sole star, Paul Mescal — currently an Emmy nominee for “Normal People” — and a jovial Mick Jagger, who appeared happy to have left the heavy lifting (or the spontaneous stunt work) to someone else.“You were obviously having so much fun in this empty hotel,” said Jagger, 77, referring to the use of the currently unoccupied Claridge’s hotel in London as a set for Mescal’s seemingly drunken shenanigans.