Rename the `suggestions` package to `code_suggestions`

What does this merge request do and why?

Step 2: This MR renames the suggestions package to code_suggestions that already contains the business logic to power the Code Suggestions AI feature.

Blocked by step 1 - !378 (merged).

How to set up and validate locally

To validate that everything was renamed correctly, you can follow the next steps:

• run tests
• build a Docker image
• run affected Makefile targets
• run the server locally or in the stg cluster

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.

Closes #290 (closed)