Filter report with new EXCLUDED_PATHS option

What does this MR do?

• introduce a new EXCLUDED_PATHS environment variable
• make this env var available in SAST & Dependency Scanning orchestrators as SAST_EXCLUDED_PATHS and DS_EXCLUDED_PATHS, respectively
• also make this env var available in SAST & DS analyzers
• filter reports and remove vulnerabilities that match the excluded paths

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/10030

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation updated for GitLab EE, if necessary
• Documentation updated in SAST
• Documentation updated in DS
• [-] Documentation 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
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer