Head & Neck Cancer Therapeutics Market Size, Share & Industry Analysis, By Drug Class (PD-1/PD-L1 Inhibitors, EGFR Inhibitors, VEGF/Angiogenesis Inhibitors, Multikinase Inhibitors, and Others), By Therapy Type (Immunotherapy, Chemotherapy, and Targeted Therapy), By Cancer Type (Head and Neck Squamous Cell Carcinoma (HNSCC/SCCHN), Nasopharyngeal Carcinoma (NPC), Differentiated Thyroid Cancer (DTC), Medullary Thyroid Cancer (MTC), Anaplastic Thyroid Cancer (ATC), and Others), By Route of Administration (Parenteral and Oral), By Distribution Channel, and Regional Forecast, 2026-2034