refactor(odbc): enhance OdbcBufferSettings and improve data fetching logic

This commit refines the OdbcBufferSettings structure to support both buffered and unbuffered modes more effectively. It updates the handling of max_column_size and batch_size, ensuring better memory management and performance tuning. The OdbcBridge is modified to streamline data fetching based on the new settings, and tests are adjusted to reflect these changes, particularly for unbuffered mode.

Author: lovasoa