Add a meaningful audit event name changes in Project CICD settings

What does this MR do and why?

This MR adds a meaningful audit event name in Project CICD settings when ever a setting is updated

Solves:

• Add a meaningful audit event name for `merge_pi... (#369316 - closed)
• Add a meaningful audit event name for `merge_tr... (#369317 - closed)

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

1. Setup audit event streaming on a group https://docs.gitlab.com/ee/administration/audit_event_streaming.html#add-a-new-streaming-destination
   1. Hint: use https://webhook.site/
2. Create a new project https://docs.gitlab.com/ee/user/project/working_with_projects.html#create-a-project
3. Change the settings for Enable merged results pipelines and Enable merge trains https://docs.gitlab.com/ee/ci/pipelines/merged_results_pipelines.html#enable-merged-results-pipelines
4. Check audit event is streamed with correct event name.

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.

Related to #369317 (closed)