Use split common packages directly

What does this MR do?

• Use broken apart command package rather than packaged common/v2/command subpackage.
• Use broken apart report package rather than packaged common/v2/report subpackage.
• Use broken apart ruleset package rather than packaged common/v2/ruleset subpackage.

The 2 packages remaining that require common as a dependency are logutil and plugin, which are both extremely stable and I don't believe they warrant extraction until we see a pressing need to update that code

What are the relevant issue numbers?

Relates to gitlab-org/gitlab#211819 (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