feat(model): Passing stop parameter to proxyllm

[fangyinc]

Description

Passing stop parameter to proxyllm

How Has This Been Tested?

Chat with all proxy LLMs.

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]

r+