Add test report summary to graphql

What does this MR do?

Adds the pipeline test report summary to GraphQL. You can access it with following query:

query getPipelineTestReportSummary($projectPath: ID!, $pipelineIid: ID!) {
  project(fullPath: $projectPath) {
    pipeline(iid: $pipelineIid) {
      id
      iid
      testReportSummary {
        total {
          time
          count
          success
          failed
          skipped
          error
          suiteError
        }
        testSuites {
          nodes {
            name
            buildIds
            totalTime
            totalCount
            successCount
            failedCount
            skippedCount
            errorCount
            suiteError
          }
        }
      }
    }
  }
}

Screenshots (strongly suggested)

Screen_Cast_2021-04-07_at_11.55.25_AM

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