Dynamic fetching of TogetherAI models (#3017)

* implement dynamic fetching of togetherai models

* implement caching for togetherai models

* update gitignore for togetherai model caching

* Remove models.json from git tracking

* Remove .cached_at from git tracking

* lint

* revert unneeded change

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Co-authored-by: Timothy Carambat <rambat1010@gmail.com>