feat(fs): introduce local file system

[zjw1111]

Purpose

Linked issue: None

Introduce the local file system implementation migrated from the Alibaba Paimon C++ repository.

This PR adds:

• local file primitives and file status wrappers
• LocalFileSystem input/output stream support
• local file system factory registration
• local file unit coverage

The requested migration scope was src/paimon/fs/local excluding CMakeLists.txt. No additional dependency files were required.

License handling:

• Replaced Alibaba-owned source headers with ASF headers.
• Checked source and target LICENSE / NOTICE; no third-party declaration updates were required for these files.

External contributor handling:

• Re-ran blame-based contributor analysis for the final file set.
• No external contributor thresholds were hit, so no Co-authored-by trailer or PR thank-you comment is needed.

Tests

API and Format

This adds local file system implementation classes under src/paimon/fs/local. It does not change public storage format or protocol.

Documentation

No documentation changes.

Generative AI tooling

Migrated-by: OpenAI Codex

[leaves12138]

I found a correctness blocker in local file creation: creating a path whose parent does not exist currently fails before it reaches the recursive Mkdirs call. Please fix this before merging.

[leaves12138]

This calls Exists(path) before creating the parent directories. For a new file under a non-existing parent (for example /tmp/a/b/file), ToFile(path).Exists() returns an IOError because access() fails with ENOENT on the missing parent path, so Create returns before lines 68-71 can create the parent directory and open the output stream. The Create path should treat missing targets as non-existing, then create parents before opening the file; otherwise FileSystem::Create only works when the parent directory already exists.

[leaves12138]

Thanks for pointing out my previous review mistake: access(..., F_OK) returns ENOENT when a parent directory is missing, so Create can continue to Mkdirs(parent). I re-reviewed the PR and found a different blocker in Rename: it validates normalized local paths but calls ::rename with the original URI strings.

[leaves12138]

This should use the normalized local paths, not the original src/dst strings. Earlier in this method, Exists(src), Exists(dst), ToFile(src), and ToFile(dst) all strip the optional file: scheme via ToFile, but the actual syscall still passes the raw URI strings to ::rename. So Rename("file:/tmp/a", "file:/tmp/b") validates /tmp/a and creates /tmp, then tries to rename a literal path named file:/tmp/a, which fails. Please call ::rename(src_file.GetAbsolutePath().c_str(), dst_file.GetAbsolutePath().c_str()) (or equivalent normalized paths).