Update OCI GenAI cohere models

[tim-slater-gt]

Description

Added the latest Cohere LLM and Embedding models offered by OCI to the list of known models.

New Package?

• Yes
• No

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes
• No

Type of Change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Not necessarily a new "feature" but it does allow use of new LLM/Embedding models.

How Has This Been Tested?

Your pull-request will likely not be merged unless it is covered by some form of impactful unit testing.

• I believe this change is already covered by existing unit tests

Suggested Checklist:

• I have performed a self-review of my own code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• I ran uv run make format; uv run make lint to appease the lint gods