Cohere support

[Avi-Robusta]

To run:

export COHERE_API_KEY=...
poetry run python3 holmes.py ask "what issues does my kubernetes cluster pods have?." --model="cohere/command-r-plus"

It looks like there are some internal issues with some of litellms functions with cohere right now this just supports model cohere/command-r-plus but other models can be included in the future by updating get_context_window_size get_maximum_output_token