premai[patch]:Standardized model init args (#21308)
[Standardized model init args
#20085](https://github.com/langchain-ai/langchain/issues/20085)
- Enable premai chat model to be initialized with `model_name` as an
alias for `model`, `api_key` as an alias for `premai_api_key`.
- Add initialization test `test_premai_initialization`
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Co-authored-by: Chester Curme <chester.curme@gmail.com>
