bitCount function support for FixedString and String data types

Why it matters

The feature extends the bitCount function to work with FixedString and String data types, allowing users to count the number of set bits (1s) in the binary representation of string data. This enhances functionality and flexibility when working with bit operations on string-based data in ClickHouse.

How to use it

Use the bitCount function directly on columns or expressions of type FixedString or String. For example:

SELECT bitCount(string_column) FROM table;