GitLab Plugin doesn't allow rebuild on comment.

### Jenkins and plugins versions report

N/A

### What Operating System are you using (both controller, and any agents involved in the problem)?

N/A

### Reproduction steps

The Jenkins GitLab integration contains the functionality to be triggered by Push, Merge Request, and Tag. But this doesn't include comments on Merge Requests. Which means you can't use the "Comment (regex) for triggering a build" functionality.

We automatically (using a script) set up all of our projects with Jenkins Integration, but doing that in an idempotent manner for a webhook isn't possible (checking if you've already added a specific webhook is tricky to impossible).

In order for this functionality to work "by default" we need the the Jenkins Integration on GitLab to notify Jenkins when a comment has occurred so that a rebuild can be triggered.

### Expected Results

When I enter the appropriate text in a comment on a Merge Request, Jenkins is triggered, without needing to set up an individual webhook.

### Actual Results

Jenkins is not triggered for a Merge Request comment.

### Anything else?

_No response_