GI Stool Testing Market Size & Forecasts 2026-2035, By Segments (Product Type, Distribution Channel, End Use, Test Type, Application), Growth Opportunities, Innovation Landscape, Regulatory Shifts, Strategic Regional Insights (U.S., Japan, China, South Korea, UK, Germany, France), and Competitive Dynamics (Quest Diagnostics, Bio-Rad Laboratories, DiaSorin, Meridian Bioscience, Sekisui Diagnostics)