Fix final prompt logging in code-suggestions

What does this merge request do and why?

There are 2 bugs in final prompt in code-suggestions:

• we are logging the structured prompt as a tuple, we should log it as a dict for better readability.
• we are using the user prompt template in place of system prompt template.

The impact of these bugs are low as we are not using the system prompt at all in code-suggestions. But it is still important to fix them.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• I've ran the affected pipeline(s) to validate that nothing is broken.
• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.