Preserve changelog events across rewrite snapshots

[osipovartem]

Summary

• walk every Iceberg snapshot in a changed-data scan range instead of relying on the final snapshot manifest list
• scan only manifests written for each snapshot sequence and expose the event snapshot sequence as a partition metadata column
• keep the ordinary table-scan path unchanged and allocate changelog ordering state only when scan_changed_data_files is enabled

Why

A final snapshot can omit file events from intermediate copy-on-write rewrites. Consumers need those events and their commit order to reduce a multi-snapshot changelog to Snowflake CHANGES(INFORMATION => DEFAULT) semantics.

Verification

• cargo +1.94.0 test -p datafusion_iceberg --lib test_changed_file_scan -- --nocapture
• cargo +1.94.0 test -p datafusion_iceberg --lib test_v3_row_lineage_columns_are_synthesized_by_scan -- --nocapture
• cargo +1.94.0 check -p datafusion_iceberg
• cargo +1.94.0 clippy -p iceberg-rust -p datafusion_iceberg --lib -- -D warnings