simplify openai base transform for chat complete

[narengogi]

noticed that the openai chat complete base transforms are missing a few parameters like top_logprobs and parallel_tool_calls

I've used the openai caht complete transformation config and I've added a line to use the default passed field (technically we only ever override the model param this way because that is the only parameter that is marked required in the transforms, but since the configs are initiated only once during the gateway spin up it is okay)

Testing done:

• [X] Verified that all the parameters present in the previous config are present in the new one
• [X] Verified the default parameter behaviour

https://github.com/Portkey-AI/gateway/issues/1421