Optionally exclude packages-dev in composer.lock files [gemnasium only]

What does this MR do?

This MR parses adds the ability to parse and optionally exclude the packages-dev section of a composer.lock file. If the DS_INCLUDE_DEV_DEPENDENCIES env var is set to false, it will exclude all of the dev dependencies.

What are the relevant issue numbers?

gitlab-org/gitlab#343041 (closed)

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
  • 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