PARIS — Simone Biles and the rest of the U.S. women’s gymnastics team walked onto the floor at Bercy Arena on Sunday in leotards adorned with thousands of crystals, the kind designed to attract as much attention as possible. Don’t mistake all that glamour — both on the floor and in the stands, where Tom Cruise and Ariana Grande were among those who took in the spectacle — for a lack of grit. The oldest team the Americans have ever brought to the Games has endured plenty through the years, from health scares to losses in their personal life.