* Updates parsers/security/common.rb to parse the `tracking`
  field if it exists
* Adds PORO and model classes for FindingFingerprint:
  * ee/lib/gitlab/ci/reports/security/finding_fingerprint.rb
  * ee/app/models/vulnerabilities/finding_fingerprint.rb
* Updates ee/app/services/security/store_report_service.rb to save
  and update finding fingerprints when storing a report in the
  database
* Adds unit tests for the new classes
* Adds unit tests for store_report_service