Heavy Duty Engines Market Size & Forecasts 2026-2035, By Segments (Vehicle Class, Horsepower, End User), Growth Opportunities, Innovation Landscape, Regulatory Shifts, Strategic Regional Insights (U.S., Japan, China, South Korea, UK, Germany, France), and Competitive Dynamics (Cummins, Daimler Truck, Volvo Group, PACCAR, Isuzu)