Allow comment on GQL vulnerabilityResolve mutation

What does this MR do and why?

This MR allows the vulnerabilityResolve GQL mutation to receive a comment field as part of the backend changes supporting &4649 (closed)

How to set up and validate locally

• On a project with vulnerabilities, enable the :deprecate_vulnerabilities_feedback feature flag.

  Feature.enable(:deprecate_vulnerabilities_feedback, Project.find(project_id))

• Note down the ID of a vulnerability that is not resolved from the Security and Compliance -> Vulnerability Report page on the project.
• Run the following query via /-/graphql-explorer

mutation($input: VulnerabilityResolveInput!) {
  vulnerabilityResolve(input: $input) {
    vulnerability {
      id
      state
      stateComment
    }
  }
}

{
  "input": {
    "id": "gid://gitlab/Vulnerability/<vulnerability_id>",
    "clientMutationId": "ANY_STRING",
    "comment": "Test Resolve Comment"
  }
}

• Check the state change and comment have been persisted:

query {
  vulnerability(id: "gid://gitlab/Vulnerability/553") {
    id
    state
    stateComment
  }
}

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 #373969 (closed)