feat(openai): add reasoning_effort option to chat completions

[agniiva]

This PR adds a new option called reasoning_effort to the OpenAI chat node. The new option allows users to constrain the reasoning effort for o1 models with supported values of low, medium, and high (default is medium). The option is added within the Options collection of the node and is configured to be sent as part of the request body.

To test:

1. Add the OpenAI chat node in n8n.
2. Enable the reasoning_effort option from the additional options and select one of the values.
3. Execute the node and inspect the outgoing request payload to ensure the reasoning_effort property is included with the selected value.
4. Verify that the response from the API is as expected when varying the reasoning_effort setting.

[CLAassistant]

All committers have signed the CLA.

[Joffcom]

Hey @agniiva,

Thanks for the PR, We have created "GHC-731" as the internal reference to get this reviewed.

One of us will be in touch if there are any changes needed, in most cases this is normally within a couple of weeks but it depends on the current workload of the team.