chore(model): Modify siliconflow name

[fangyinc]

Description

• Change all 'silicon_flow' to 'siliconflow'
• Fix the bug of max_chunks_once_load and max_threads missing

How Has This Been Tested?

See 《DB-GPT + SiliconCloud 使用文档》

Snapshots:

Include snapshots for easier review.

Checklist:

• My code follows the style guidelines of this project
• I have already rebased the commits and make the commit message conform to the project standard.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules

[Aries-ckt]

LGTM.

[csunny]

Cool，LGTM