feat(telemetry): add code suggestions token tracking telemetry

What does this merge request do and why?

Why we don't have token_per_user in tableau dashboard?

answer:

The ai_gateway event doesn't have the attached user id that get's anomyzed into gsc_pseudoanomyzed_user_id and counted so unfortunately no.

https://gitlab.com/gitlab-org/gitlab/-/issues/471342#note_2036144581

In this MR we add user_id.

How to set up and validate locally

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

Merge request checklist

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