JERUSALEM — Israel came to a standstill on Monday as people stopped in their tracks for a two-minute siren that wailed across the country in remembrance of the Holocaust’s 6 million Jewish victims. Pedestrians stood in place, buses stopped on busy streets and cars pulled over on major highways — their drivers standing on the roads with their heads bowed. A wreath-laying ceremony at the Yad Vashem Holocaust memorial followed, with Israeli leaders and Holocaust survivors in attendance. Other ceremonies, prayers and musical performances took place in schools, community centers and army bases around the country. Restaurants, cafes and places of entertainment shut down, and radio and TV programs were dedicated almost exclusively to documentaries about the Holocaust, interviews with survivors and somber music.