By Francesca Street, CNN Côte d’Azur, France (CNN) — Kat Jamieson slid open the doors to her poolside hotel room in Saint-Tropez and was greeted with an unexpected sight: cameras and a film crew surrounding actor Laura Dern, who was holding court in front of the rippling blue water. “She was wearing this fabulous Missoni caftan,” Jamieson tells CNN Travel. Jamieson couldn’t believe it. Not only was she witnessing an Oscar-winning actor at work, …