Add ability to comment on violations
## Overview
As part of the [Detail view for Violations epic](https://gitlab.com/groups/gitlab-org/-/epics/17780), this issue focuses on adding a details sidebar for when the user clicks on the audit event.
### Design
Design issue: https://gitlab.com/gitlab-org/gitlab/-/issues/463865+


### Implementation tasks
- [x] Comments should be included in the system notes graphql query
- [x] Use the [shared Field component](app/assets/javascripts/vue_shared/components/markdown/field.vue) for creating a new note
- [x] Reuse or create a component similar to [WorkItemDiscussion](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/work_items/components/notes/work_item_discussion.vue) to show a discussion thread in the system notes
- [x] GraphQL mutation to add a note/thread/etc.
#### GraphQL query
TBD
issue