Add comment to AI feedback

What does this MR do and why?

This MR adds support for including comments in the AI feedback submission to explain vulnerability.

Note: There is an issue to standardize the feedback component, so this solution serves as an interim until that issue is resolved.

Screenshots or screen recordings

user-feedback-form

Before	After
	With selection

How to set up and validate locally

1. Enable the openai_experimentation, ai_experimentation_api, and explain_vulnerability feature flags.
2. Clone this project: https://gitlab.com/gitlab-examples/security/security-reports
3. Run a pipeline against the master branch.
4. Go to Security -> Vulnerability report.
5. Click on a vulnerability to go to the details page.
6. Click on "Try it out" to open "Explain this vulnerability" drawer

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 #413693 (closed)