Use DAST_TARGET in conjunction with DAST_URLS

What does this MR do?

DAST can run on many different environments and sometimes the Host for that environment isn't known until runtime, for example, run running DAST on a review apps. Rather than add a before script to change the host of every URL in DAST_URLS, this MR changes DAST_URLS to DAST_PATHS which will include a list of paths and the build the URL using the DAST_WEBSITE env variable.

This MR is the action taken based on this comment: 214120#note_410597079

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer