### What problem does this PR solve?
When parsing documents containing images, the current code uses a
single-threaded approach to call the VL model, resulting in extremely
slow parsing speed (e.g., parsing a Word document with dozens of images
takes over 20 minutes).
By switching to a multithreaded approach to call the VL model, the
parsing speed can be improved to an acceptable level.
### Type of change
- [x] Performance Improvement
---------
Co-authored-by: liuzhenghua-jk <liuzhenghua-jk@360shuke.com>
2f768b96e8