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 PD-L1-positive