SystemCheck library (EE part)

What does this MR do?

• Solves MR issue from EE gitlab-org/gitlab-ce!9173
• Refactor Elasticsearch checks to SystemCheck

Are there points in the code the reviewer needs to double check?

Must be in sync with gitlab-org/gitlab-ce!9173

Why was this MR needed?

MR gitlab-org/gitlab-ce!9173 did not apply cleanly, also there were EE specific checks in the same namespace that required a refactor to the new library.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

• gitlab-org/gitlab-ce#28080
• gitlab-org/gitlab-ce!9173