format_table: fix writes when partition columns are reordered

[shyjsarah]

Summary

Fix Format Table writes when a partition column is not the first field in the table schema. The writer previously combined full-schema column indices with partition-only field metadata, which could panic with an out-of-bounds access.

Changes

• use full table schema metadata when extracting partition values from Arrow batches
• add a REST catalog regression test with the partition column at the end of the schema
• keep the change internal; there is no public API change

Testing

• cargo test -p paimon-datafusion --test rest_format_table_dml
• cargo clippy -p paimon-datafusion --test rest_format_table_dml -- -D warnings
• cargo fmt --all -- --check

[JingsongLi]

+1