[Model] Refactor Step3-VL processor to HF style

[DarkLight1337]

Purpose

• Make Step3-VL processor contain image_processor in order to fit HF call semantics.
• Make Step3-VL more efficient by avoiding unnecessary text/token construction and string concatenation
• Fix a typo in InternVL and Kimi-K2.5 processor

Test Plan

Checked using the example script

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request refactors the Step3-VL processor to align with the Hugging Face style by separating the image processing logic into its own class. While the refactoring is a good step towards better code organization, I've identified a critical bug in the new processor's __call__ method that would cause a runtime error. Additionally, there's a high-severity functional regression due to the removal of a method, which results in less accurate image token counting. I have provided detailed comments and code suggestions to address both of these issues.

[DarkLight1337]

Ready for review