[FE] - Add mocked PipelineSecurityFinding data

Add mocked PipelineSecurityFinding data (don't use it, but set up mocked gitlab service function and Typescript Data Structure as well as mocked finding data in entities.ts) (Can be done in parallel)

See: !871 (closed) for reference

Estimation covers:

1. Hit production test project to grab sample response
2. Add mocked data to entities.js, add Typescript Types
3. Add unit tests

Use #721 (closed) as reference and !802 (merged)

From @djadmin:

I'm posting the graphql query we can use to pull the vulnerability details based on the UUIDs. I also picked up a public repo for known findings.

query pipelineFinding($fullPath: ID!, $pipelineId: ID!, $uuid: String!) {
  project(fullPath: $fullPath) {
    id
    pipeline(iid: $pipelineId) {
      id
      securityReportFinding(uuid: $uuid) {
        id: uuid
        vulnerability {
          id
          description
          descriptionHtml
        }
      }
    }
  }
}

query variables

{
  "fullPath": "gitlab-org/security-products/demos/dast/dvwa",
  "pipelineId": "12",
  "uuid": "da3c6db0-f38f-5b01-b82f-8f36094a025c"
}