Migrate i_code_review_user_approve_mr to snowplow

What does this MR do and why?

Related to #362281 (closed)

We're moving counters from Service Ping to Snowplow. i_code_review_user_approve_mr is one of the counters that we want to move.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally

1. Enable snowplow micro
2. Approve an MR
3. Check if a new event with i_code_review_user_approve_mr action has been registered at localhost:9090/micro/good

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.