fix: Make FileLock robust to the CWD (Fix #2252)

[Prathmesh010190]

Description

This PR fixes Issue #2252 by making FileLock path handling robust to the Current Working Directory (CWD).

The previous implementation used os.path.join, which could incorrectly anchor absolute paths to the current working directory in certain scenarios. This change replaces that logic with url2pathname, ensuring that absolute paths are handled correctly and consistently.

Motivation and Context

Fixes #2252.

This change prevents FileLock from incorrectly resolving lock file paths relative to the current working directory, improving reliability when working with absolute paths.

How Has This Been Tested?

• Verified that the modified code correctly handles absolute paths.
• Pass the test by running: pytest qlib/tests/test_all_pipeline.py
• If you are adding a new feature, test on your own test scripts.

Screenshots of Test Results (if appropriate)

1. Pipeline test: Not run.
2. Your own tests: Verified path resolution behavior manually.

Types of changes

• Fix bugs
• Add new feature
• Update documentation