Parse requirements reports

What does this MR do?

This is the first iteration of connecting tests with requirements.

User can add a CI job which (if triggered) creates "passed" test report for each existing requirement. IOW job's semantic is: "I confirm that all requirements are met" (in the next iteration we will extend this to set status for specific requirements.

An example of CI yml config:

default:
  when: manual
  script:
    - mkdir tmp
    - echo "{\"*\":\"passed\"}" > tmp/artifacts.json
  artifacts:
    reports:
      requirements: tmp/artifacts.json

Documentation will be updated separately (tracked by #215510 (closed)).

Because this is an opt-in feature (user has to explicitly add the specific CI job), feature flag is not necessary.

Related to #215513 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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