Add 2026 Index holidays to MHDB (#9152)

* Add index-usa-[*] holidays and early closes

* Add Index-spx 2026-2027 holidays & early closes

* Add 2026 Index-ndx holidays & early closes

* Add 2026 Index-VIX holidays and early closes

* Add EUREX Index holidays 2026-2030

* Add index HKFE 2026 holidays and early closes

* Add 2026 Index-OSE holidays and early closes

* Add missing 2026 Index-India NSE holidays

* Address suggested changes

Author: Marinovsky