Add 'think' option to control reasoning models' thinking behavior

[mvawork]

This update introduces the 'think' option, allowing users to dictate whether the model deliberates before responding.

Key modifications:

• Incorporated the think field into the OllamaOptions.
• Developed the necessary logic to process this new setting.

This addition enriches the OllamaChatModel, offering greater command over the model's operations, which will be particularly beneficial for sophisticated applications.

[sunyuhan1998]

Thank you for your contribution! However, it appears this is a duplicate PR, as this improvement is already being worked on in #3386.

[mvawork]

I'll wait for the feature to be implemented. For now, I'll use my workaround.