Carole Radziwill Rejoining 'RHONY' as a 'Friend' for Season 16

Major reality TV shakeup -- Carole Radziwill is heading back to "The Real Housewives of New York City" ... but pump the brakes, she’s not reclaiming her apple full-time. TMZ has confirmed Carole -- who held court from S5 through 10 -- is…