Add ability to add comments to vulnerability state history entries

What does this MR do?

NOTE: This MR requires that !29437 (merged) be merged first.

This MR adds the ability to add, edit, and delete a comment for a vulnerability state history entry on the standalone vulnerability page:

How the feature works

When there's no comment, it will show the "Add a comment" button

When there's a comment, it will show the comment and the edit/delete buttons

When the edit button is clicked, it will show the textarea to edit the comment and the save and cancel buttons

When the delete button is clicked, it will show the delete confirmation buttons

While the comment is being saved, the textarea, save, and cancel buttons are disabled and a spinner is shown

While the comment is being deleted, the delete and cancel buttons are disabled and a spinner is shown

How to test locally

https://gitlab.com/snippets/1956676

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry NOT REQUIRED, THIS IS CURRENTLY BEHIND A FEATURE FLAG
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done