### 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

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Co-authored-by: liuzhenghua-jk <liuzhenghua-jk@360shuke.com>