Add delete button in edit more for incident timeline events #372265

What does this MR do and why?

In the incident view, add a new button (Delete button) to delete events from the timeline in the edition form.

Although there is already the possibility of deleting in another view, this gives the user a new alternative.

Screenshots or screen recordings

URL ~/issues/incident/id

How to set up and validate locally

From the implementation guide

1. Ensure you are running enterprise edition
2. Go to a project's settings, then Monitor
3. Create an incident or open an existing one
4. Navigate to Timeline tab
5. Toggle a dropdown button on a timeline item and select Edit

Test spec

yarn jest spec/frontend/issues/show/components/incidents/edit_timeline_event_spec.js spec/frontend/issues/show/components/incidents/timeline_events_form_spec.js

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 #372265 (closed) Closes #372265 (closed)