fix: resolve URI schemes in ArrowFileSystemFileIO before opening files

[smaheshwar-pltr]

Issue

Closes #7

When reading Avro or Parquet files on S3 via ArrowFileSystemFileIO, the readers call io->fs()->OpenInputFile() directly on the underlying Arrow filesystem, bypassing ResolvePath(). This means s3:// prefixes are never stripped. Arrow's S3FileSystem expects bare bucket/key paths, not full URIs.

Consumers using iceberg-cpp to scan tables with S3-backed storage hit:

Invalid: Expected an S3 object path of the form 'bucket/key...', got a URI:
's3://warehouse/default/test_table/metadata/snap-487842974509551922-0-dc0a55d6-5df1-4ffa-a01c-b7481e5c663c.avro'

PR

When reading or writing Avro/Parquet files on S3 via ArrowFileSystemFileIO, the file path includes the URI scheme (e.g., s3://bucket/key). Arrow's S3FileSystem expects bare paths (bucket/key). ArrowFileSystemFileIO::ResolvePath() handles this stripping in ReadFile/WriteFile/DeleteFile, but the Avro and Parquet readers/writers bypass FileIO and call io->fs()->OpenInputFile() / io->fs()->OpenOutputStream() directly — skipping ResolvePath() entirely.

This causes S3 file operations to fail when going through the Avro/Parquet code paths (e.g., manifest reads).

Fix

Add OpenInputFile() and OpenOutputStream() public methods to ArrowFileSystemFileIO that apply ResolvePath() before delegating to the underlying Arrow filesystem. Update all four reader/writer call sites (avro_reader, avro_writer, parquet_reader, parquet_writer) to use the new methods instead of calling fs() directly.

This keeps URI resolution encapsulated in one place rather than scattered as manual :// stripping in each reader/writer.

[smaheshwar-pltr]

Closing — this fix has been superseded by upstream commit fc80e4b (feat(io): add streaming FileIO support, apache#641). ArrowFileSystemFileIO::NewInputFile/NewOutputFile and the new OpenArrowInputStream/OpenArrowOutputStream helpers now call ResolvePath() for the URI fast-path, and all four reader/writer call sites (avro/parquet × read/write) have been updated to use them. No remaining gap.