Enhance the default column handling

When new columns are added to a pinot table, the server is able to automatically generate default columns for the new added columns. There are 2 types of default column that can be auto-generated:

1. New added column without transform function: default column will be filled with default null value (always dictionary encoded)
2. New added column with transform function (derived column): default column will be filled with values calculated based on the transform function

There are 2 things not handled right now:

1. Generate default column raw forward index (not dictionary encoded)
2. Support transform function on another new added column: we need to calculate the dependency between new added columns, and generate them in sequence

See BaseDefaultColumnHandler for details