Added RuboCop cops for checking DB migrations

What does this MR do?

This MR adds two RuboCop cops for checking migrations

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

Yes, the code and whether we actually want this or not. Also, do we want tests for cops or not? If so, how on earth do you test cops?

Why was this MR needed?

While generated migrations tell developers to use certain methods there's no tool that automatically enforces this.

What are the relevant issue numbers?

Not directly related but it lead me to adding this: #14545 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added Doesn't affect end-users
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

cc @rspeicher @dzaporozhets