Allow to filter requirements by missing status

What does this MR do?

Allows to filter requirements with missing status on GraphQL, which means requirements without test reports.

Sample GraphQL query

query requirements {
  project(fullPath: "flightjs/flight") {
    requirements(lastTestReportState: MISSING) {
      edges {
        node {
          id
          title
        }
      }
    }
  }
}

SQL query executed

SELECT "requirements".* 
FROM   "requirements" 
       LEFT OUTER JOIN "requirements_management_test_reports" 
          ON "requirements_management_test_reports"."requirement_id" = "requirements"."id" 
WHERE  "requirements"."project_id" = 278964
       AND "requirements_management_test_reports"."requirement_id" IS NULL 
ORDER  BY "requirements"."id" DESC 

• Query plan: https://explain.depesz.com/s/6wJm

related to #224614 (closed)