U.S. Prescription Drugs Market Size, Share & COVID-19 Impact Analysis, By Product Type (Generic Drugs, Orphan Drugs, and Other Prescription Drugs), By Therapy Area (Oncology, Central Nervous System, Vaccines, Immunosuppressants, and Others), By Distribution Channel (Hospital Pharmacies, Retail Pharmacies & Drug Stores, and Online Pharmacies), and Country Forecast, 2023-2030