Boiler Turbine and Generator (BTG) Market Size & Forecasts 2026-2035, By Segments (Application, Fuel Type, Component Type), Growth Opportunities, Innovation Landscape, Regulatory Shifts, Strategic Regional Insights (U.S., Japan, China, South Korea, UK, Germany, France), and Competitive Dynamics (General Electric, Siemens Energy, Mitsubishi Power, Doosan Heavy Industries, Alstom)