Update DAST-On-Demand-API-Scan CI Tmplt with 15.0 changes

Issue

Related to #363237 (closed)

Summary

• Update template: DAST-On-Demand-API-Scan.gitlab-ci.yml
  • Update version from 1 to 2
  • Update image from api-fuzzing to api-security
  • Add new setting DAST_API_IMAGE_SUFFIX
  • repository image name based on new setting and values
• Add dast_on_demand_api_scan_gitlab_ci_yaml_spec.rb to test template
  • Check template use expected registry: version, name and prefix
  • Check computed image name

Test Project

• Project https://gitlab.com/herbmadrigal/issue-363237
  • .gitlab-ci.yml
  • Pipeline