Global Garden Rooms Market Size, Share & Demand Report By Product Type (Standalone Garden Rooms, Attached Garden Rooms, Modular/Prefabricated Garden Rooms, Custom-Built Garden Rooms), By Construction Method (Prefabricated, On-site Constructed), By End Use (Residential, Commercial, Institutional), By Distribution Channel (Direct-to-Consumer, Contractors & Builders, Online Platforms), By Region & Segment Forecasts, 2025–2030