Support in JOIN ON section filters that affect columns from only one table. For use case see
https://stackoverflow.com/questions/5284929/mysql-left-join-with-optional-value-in-second-table

Now it's only move such conditions from ON section to WHERE, but we need to handle this filters inside join implementation. It will also fix #21671