Add visual indicator if DAST failed to scan a URL

This is a follow-up issue to #11024 (comment 248512924). #11024 (closed) adds a count of how many URLs have been scanned.

Currently, there is no visual indication in case DAST is running into a problem when scanning a particular URL.

For example, take this report https://gitlab-org.gitlab.io/-/gitlab/-/jobs/354724333/artifacts/gl-dast-report.json. The corresponding test run was running into a problem when scanning a URL:

      "urlsIoError": [
        {
          "url": "https://gitlab-review-sa-pat-exp-6uagk5.gitlab-review.app/robots.txt",
          "statusReason": "ZAP IO Error",
          "reasonNotProcessed": "I/O Error",
          "processed": "false",
          "messageId": "7",
          "method": "GET",
          "statusCode": "400"
        },
        ...

If DAST encounters an error scanning a URL, there should be some visual clue indicating this circumstance in the UI. urlsIoError should not be counted towards the total number of scanned URLs.

/cc @andyvolpe