GH-41365: [Python] Fix S3 URI with whitespace silently falling back to LocalFileSystem

[ernestprovo23]

Rationale

Closes #41365

When _resolve_filesystem_and_path() receives an S3 URI containing spaces (e.g. s3://bucket/path with space/file), the C++ URI parser raises ValueError("Cannot parse URI"). The Python code previously caught all "Cannot parse URI" errors and silently fell back to LocalFileSystem, producing a confusing downstream error instead of the real parsing failure.

What changed

1. Added _is_likely_uri() helper — a Python port of the C++ IsLikelyUri() heuristic from cpp/src/arrow/filesystem/path_util.cc. It checks whether a string has a valid URI scheme prefix (2-36 chars, RFC 3986 compliant).

2. Modified error handling in _resolve_filesystem_and_path() — the except ValueError block now distinguishes:

   • "empty scheme" → still falls back to LocalFileSystem (no scheme at all)
   • "Cannot parse URI" + _is_likely_uri() returns False → still falls back (not a URI, just a local path)
   • "Cannot parse URI" + _is_likely_uri() returns True → re-raises the error (it IS a URI, just malformed)

3. Changed raise e to raise — preserves the original traceback (minor style improvement).

Tests added

• test_is_likely_uri() — unit tests for the heuristic covering valid schemes (s3://, gs://, hdfs://, abfss://, grpc+https://), local paths, Windows drives, and invalid prefixes.
• test_resolve_filesystem_and_path_uri_with_spaces() — verifies S3/GCS/ABFSS URIs with spaces now raise ValueError.
• test_resolve_filesystem_and_path_local_with_spaces() — verifies local paths with spaces still return LocalFileSystem.

Test plan

• All new tests pass (14/14)
• Manual verification: _resolve_filesystem_and_path("s3://bucket/path with space") raises ValueError
• Manual verification: _resolve_filesystem_and_path("/local/path with space") returns LocalFileSystem
• Existing test_fs.py tests pass (requires full C++ build environment)

• GitHub Issue: [Python] Pyarrow fs incorrectly resolves S3 URIs with white space as a local path #41365

[github-actions]

⚠️ GitHub issue #41365 has been automatically assigned in GitHub to PR creator.

[rok]

Hey @ernestprovo23, thanks for working on this and opening the PR. I'll kick off the CI run and hopefully I or someone else wil find time early next week to do a review.

[rok]

You mention on the issue:

Working on a fix that ports the C++ IsLikelyUri() heuristic to Python and uses it in _resolve_filesystem_and_path()

Could you check if it's possible to expose IsLikelyUri through Python so ultimately the logic is only implemented once and is always doing the same?