Added Functions Left, Right, Trim, Ltrim, Rtrim, Timestampadd, Timestampsub for SQL Standard Compatibility

Why it matters

These functions enhance ClickHouse's SQL compliance by providing commonly used string manipulation and timestamp arithmetic functions. This enables users migrating from other SQL databases or writing standard SQL queries to use familiar functions, improving usability and interoperability.

How to use it

Users can directly use the new functions in their queries like left(string, n), trim(string), or timestampadd(unit, interval, timestamp) without any special configuration, as they are now part of ClickHouse's built-in function set.