Switched to AzureOpenAI for api_type=="azure" (#1232)

* Switched to AzureOpenAI for api_type=="azure"

* Setting AzureOpenAI to empty object if no `openai`

* extra_ and openai_ kwargs

* test_client, support for Azure and "gpt-35-turbo-instruct"

* instruct/azure model in test_client_stream

* generalize aoai support (#1)

* generalize aoai support

* Null check, fixing tests

* cleanup test

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Co-authored-by: Maxim Saplin <smaxmail@gmail.com>

* Returning back model names for instruct

* process model in create

* None check

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Co-authored-by: Chi Wang <wang.chi@microsoft.com>