General QA refactoring

What does this MR do?

• Favor data-qa selectors
• Add required elements to Snippet::Show page
• Add dataset argument to render_label in LabelHelper
  • Since this is simply pass-through - I'm not sure this requires a test to be written in labels_helper_spec

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content