Update OpenAI provider to OpenAI Python SDK 2.x

[kaxil]

Raise the openai[datalib] floor to >=2.37.0 so the provider builds against the current 2.x SDK line, and refresh stale default models (gpt-3.5-turbo -> gpt-4o-mini, text-embedding-ada-002 -> text-embedding-3-small).

Related:

• Add Workload Identity authentication to OpenAI provider #69069
• Add OpenAI Responses and Conversations support #69070
• Deprecate OpenAI Assistants and Threads hook methods #69071

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