Return Structured ColumnCloseResult from GenericColumnWriter::close

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

ColumnCloseResult is currently defined as

type ColumnCloseResult = (
    u64,
    u64,
    ColumnChunkMetaData,
    Option<ColumnIndex>,
    Option<OffsetIndex>,
);

Not only is this type alias not public, but it isn't immediately apparent what fields are which.

Describe the solution you'd like

/// Metadata returned by [`GenericColumnWriter::close`]
#[derive(Debug, Clone)]
pub struct ColumnCloseResult {
    /// The total number of bytes written
    pub bytes_written: u64,
    /// The total number of rows written
    pub rows_written: u64,
    /// Metadata for this column chunk
    pub metadata: ColumnChunkMetaData,
    /// Optional column index, for filtering
    pub column_index: Option<ColumnIndex>,
    /// Optional offset index, identifying page locations
    pub offset_index: Option<OffsetIndex>,
}

Describe alternatives you've considered

Additional context