Added ISO Year Support in formatDateTime Function

Why it matters

This feature enables users to format dates using ISO year representations according to the ISO week date system. It solves the limitation where only calendar year formats were supported, allowing more accurate and standardized date formatting based on ISO year standards.

How to use it

Use the formatDateTime function with the new format specifiers %g for the two-digit ISO year or %G for the four-digit ISO year in the format string. For example:

SELECT formatDateTime(now(), '%G-%m-%d');