Add audit logs when assigning CI runner to project

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR adds audit log entries when assigning a runner to a new project.

Screenshots or screen recordings

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How to set up and validate locally

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

1. Go to a project's CI/CD settings page (e.g. http://gdk.test:3000/h5bp/html5-boilerplate/-/settings/ci_cd) and expand the Runners section

2. Use the runner registration token listed to register a runner:

   gitlab-runner register -config ~/.gitlab-runner/config.gdk.toml \
           --executor "shell" \
           --url "http://gdk.test:3000/" \
           --description "Project audit log test runner" \
           --tag-list "shell,gdk,test" \
           --run-untagged="false" \
           --locked="false" \
           --access-level="not_protected" --non-interactive \
           --registration-token="$REGISTRATION_TOKEN"

3. Go to another project's CI/CD Settings page (e.g. http://gdk.test:3000/flightjs/Flight/-/settings/ci_cd) and expand the Runners section

4. In the Available specific runners section, you should find the new runner listed

5. Click on the Enable for this project button

6. Visit http://gdk.test:3000/admin/audit_logs and see the related audit log entry

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.

Part of #349542 (closed)