Add Support for Inserting Avro Nested Fields

Why it matters

To enable users to efficiently insert data with nested structures from Avro files into ClickHouse tables, improving compatibility and simplifying ETL processes involving complex Avro schemas.

How to use it

When inserting data from Avro format, nested fields within the Avro schema are now supported automatically. Simply use the INSERT INTO statement with the FORMAT Avro clause on tables that have nested columns, and ClickHouse will correctly parse and insert the nested data.