Global Irritable Bowel Syndrome Treatment Market By Type (IBS-D, IBS-C, IBS-S, and IBS-U), By Drug Class (Linzess/Constella, Xifaxan, Viberzi, Amitiza, and Others), By Distribution Channel (Hospital Pharmacy, Retail Pharmacy, and Others), By Region, and Key Companies - Industry Segment Outlook, Market Assessment, Competition Scenario, Trends and Forecast 2025-2034