feat: missing type for batch request input and output objects

[NikkiAung]

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Changes being requested

Developed types feat req for missing type for batch request input and output objects

src/openai/types/__init__.py
src/openai/types/batch_request_input.py
src/openai/types/batch_request_output.py

Additional context & links

https://platform.openai.com/docs/api-reference/batch/request-input https://platform.openai.com/docs/api-reference/batch/request-output

Fixed #1937