Function build_sources

fn build_sources(
    stream_ctx: &Arc<StreamContext>,
    part_range: &PartitionRange,
    compaction: bool,
    part_metrics: &PartitionMetrics,
    range_builder_list: Arc<RangeBuilderList>,
    sources: &mut Vec<Source>,
)

Builds sources for the partition range and push them to the sources vector.