refactor(fs): make FileStatus and BasicFileStatus concrete value types

[lucasfang]

refactor(fs): make FileStatus and BasicFileStatus concrete value types

Purpose

Linked issue: close #xxx

FileStatus and BasicFileStatus were pure-virtual interfaces with one
subclass per file system implementation (Local/Jindo/ObjectStore/Mock),
forcing a heap allocation per entry on every GetFileStatus /
ListFileStatus / ListDir call. None of the subclasses added any
behavior or extra state beyond path / length / is_dir /
modification_time, so the polymorphism was not pulling its weight.

This change turns both classes into concrete value types (similar to
arrow::fs::FileInfo):

• FileStatus holds path, length, is_dir and modification_time; all
  virtual methods (including the destructor) are removed.
• BasicFileStatus holds path and is_dir; all virtual methods are removed.
• FileSystem::GetFileStatus now returns Result<FileStatus>;
  ListFileStatus fills std::vector<FileStatus>*; ListDir fills
  std::vector<BasicFileStatus>*.
• The four subclasses (LocalFileStatus, JindoFileStatus,
  ObjectStoreFileStatus, MockFileStatus) and three basic subclasses
  (LocalBasicFileStatus, JindoBasicFileStatus,
  ObjectStoreBasicFileStatus) are deleted; local_file_status.h and
  jindo_file_status.h are removed.
• Jindo converts JdoFileInfo to paimon types eagerly instead of lazily
  wrapping it.

No behavioral semantics change: unknown modification time still reports
kUnknownModificationTime, directory semantics are unchanged, and
ListDir still returns basic information only.

Tests

No new cases added; existing coverage exercises the changed paths:

• file_system_test.cpp (ListDir / GetFileStatus / ListFileStatus for
  local and object store), object_store_file_system_test.cpp,
  resolving_file_system_test.cpp, jindo_file_system_test.cpp
• Core suites: orphan_files_cleaner, file_store_commit_impl (gmock
  FileSystem), snapshot_manager, manifest_file, merge_tree_writer,
  lookup_levels, append_only_writer, commit_message, etc.
• Integration suites: read/write/scan/clean/pk-compaction inte tests

API and Format

Yes, this is a breaking C++ API change in include/paimon/fs/file_system.h:

• FileStatus / BasicFileStatus are no longer polymorphic and cannot
  be subclassed; they are now passed by value.
• FileSystem::GetFileStatus signature changes from
  Result<std::unique_ptr<FileStatus>> to Result<FileStatus>;
  ListFileStatus and ListDir out-parameters change from
  std::vector<std::unique_ptr<...>>* to std::vector<...>*.
• Third-party FileSystem implementations must update their overrides.

No effect on storage format or wire protocol.

Documentation

No new feature; only class doc comments were updated to reflect value
semantics.

Generative AI tooling

Generated-by: Qoder

[lxy-9602]

+1

[SteNicholas]

LGTM.