Add tqdm to _litellm.py

[NFrnk]

What does this PR do?

This PR adds tqdm to the litellm representation model, similar to other LLM representation models like OpenAI or llamacpp to better track the progress of the requests.

Fixes #2407

Before submitting

• This PR fixes a typo or improves the docs (if yes, ignore all other checks!).
• Did you read the contributor guideline?
• Was this discussed/approved via a Github issue? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes (if applicable)?
• Did you write any new necessary tests?

[MaartenGr]

Awesome, LGTM! Thank you for the work on this.