Expose dismissal reason and dismissal descriptions in Vulnerability details view

What does this MR do?

This MR expose dismissal_reason, dismissal_descriptions from Vulnerability::Feedback. Though it was mentioned in the issue, to expose comment as well, this MR does not include that intentionally as it was already exposed as a part of comment_details. This MR includes spec to make sure we can access comment.

• Extend helper to return dismissal feedback
• Expose dismissal_reason and dismissal_descriptions in feedback entity
• Update spec factory to accommodate dismissal reason
• Update graphql doc
• Add newly externalized strings
• Add change log

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because _____.
• 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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #296855 (closed)