Cephalosporin Market, by Generation (First-generation, Second-generation, Third-Generation, Fourth-Generation, and Fifth-Generation), Type (Branded and Generic), Route of Drug Administration (Intravenous and Oral), and Application (Respiratory Tract Infection, Skin Infection, Ear Infection, Urinary Tract Infection, and Sexually Transmitted Infection): Global Opportunity Analysis and Industry Forecast, 2019-2027