CHARLOTTE, N.C. — Reneé Rapp had a pretty extraordinary 2023, starting last January with a sold-out concert for 2,300 fans of her pop music at the O2 Forum Kentish Town in London and ending in December with her being named one of the Associated Press’ five “breakthrough entertainers of the year.” And 2024 almost surely will wind up being even bigger for the 23-year-old Huntersville native. It’ll open with a double-whammy of splashy opportunities for her to build her following. On Jan. 12, the movie-musical version of “Mean Girls” lands in theaters with Rapp atop the marquee; then on Jan. 20, s…