Decode Hive partition values in listing tables

[Kevin-Li-2025]

Which issue does this PR close?

• Closes Partition values are not URL-decoded when extracted from Hive-style paths #19650.

Rationale for this change

Hive-style partition values can contain percent-encoded characters in object-store paths, such as %2F for / or %20 for a space. parse_partitions_for_path currently returns those encoded bytes literally, so listing tables expose foo%2Fbar instead of foo/bar.

What changes are included in this PR?

• Percent-decode extracted partition values in parse_partitions_for_path.
• Return Cow<str> from the parser so unchanged values keep the borrowed fast path and decoded values can be owned only when needed.
• Fall back to the original raw partition value if percent decoding does not produce valid UTF-8, rather than dropping the file from listing results.
• Add helper-level and PartitionedFile conversion tests for decoded partition values.

Are these changes tested?

• cargo fmt --all --check
• cargo test -p datafusion-catalog-listing