bug: TableScanBuilder should take care of empty projections

[sundy-li]

For query select count() from table, the project is empty, so table should not scan any columns and return an RecordBatch with empty arrays and the true row count (by parquet metadata).

Yet it scans all columns.

// Empty column names means to select all columns
    column_names: Vec<String>,

 /// Select all columns.
    pub fn select_all(mut self) -> Self {
        self.column_names.clear();
        self
    }

[sundy-li]

/assign me

[Xuanwo]

Thank you @sundy-li for working on this!