A Phase 3, Double-blind, Randomized Study of Zolbetuximab in Combination with Pembrolizumab and Chemotherapy (CAPOX or mFOLFOX6) in First-line Treatment of Locally Advanced Unresectable or Metastatic Gastric or Gastroesophageal Junction Adenocarcinoma in Participants Whose Tumors are HER2-negative, Claudin (CLDN) 18.2-positive and Programmed Death-ligand 1 (PD-L1)-positive. A Study of Zolbetuximab Together with Pembrolizumab and Chemotherapy in Adults with Gastric Cancer.