U.S. Physician Groups Market Size, Share & Industry Analysis, By Number of Physicians (2 to 10, 11 to 24, 25 to 50, and More than 50), By Ownership (Physician-owned, Hospital-owned, and Others), By Specialty (Primary Care, Pediatrics, OB/GYN, Ophthalmology, Orthopedics, Psychiatry, Cardiology, Dermatology, and Others), By Payor (Public Health Insurance and Private Health Seguro/fuera de su bolsillo), por tipo (especialidad única y multipecialidad), por región (noreste, sureste, suroeste, medio oeste y oeste), y pronóstico de países, 2025-2032