Support setting llm provider in Canvas of LangSmith

[YannLex]

Checked

• I searched existing ideas and did not find a similar one
• I added a very descriptive title
• I've clearly described the feature request and motivation for it

Feature request

As playground support setting LLM Provider, I prefer to set it to my hosted LLM, but canvas not support it.

Motivation

This feature will let our team manage llm key strictly.

Proposal (If applicable)

No response