Add file_type to DataFile structure

[chenjunjiedada]

Per the merge on read design doc: https://docs.google.com/document/d/1FMKh_SQ6xSUUmoCA8LerTkzIxDUN5JbStQp5Hzot4eo/edit, In order to support row-level delete, we need to add a deletion type to DataFile structure.

[chenjunjiedada]

@openinx FYI, Just change the title for naming since the deletion file is a data file too, so using file_type would be more clear, I removed data prefix because the data structure is already data_file.

And it should be defined as optional since there may be existing data files in the table. The actual stored values of file_type could be:

• null: normal data file that has the defined table schema, the default value
• 0: normal data file that has the defined table schema
• 1: file and position based deletion data file that has the schema (_file, _pos)
• 2: column equality-based deletion data file that has the schema (_field_id, _value)

The read values should be (0, 1, 2), though.

[chenjunjiedada]

This is resolved by #1030.