General Motors said it would delay plans for a new Buick electric vehicle and push back the opening of an EV truck factory, the latest retrenchment by automakers that had been pushing hard into battery-powered cars. GM Chief Executive Mary Barra told Wall Street analysts Tuesday that GM is deferring investments to ensure the company doesn’t get ahead of demand. For years, automakers raced to invest in new battery plants and factory upgrades to introduce new electric models, encouraged by early consumer enthusiasm.