[FEAT]: Add the option to switch between thinking modes in the deepseek model

[chenze123abc]

What would you like to see?

Add the option to toggle the thinking mode in the deepseek model. Currently, there is no setting to disable the thinking mode.

[timothycarambat]

@angelplusultra can you confirm that #5584 includes DeepSeek?
If not, lets extend that PR to this endpoint as well to support this.

The tie back this issue to that PR so both close when the PR is merged.