Better error for new operation run

When switching to the new operations, you may forget to remove the yield, and this causes a confusing error saying you need to define run. But you may look at it and say "I did..".

To get around this, we could make run not abstract and instead just make it raise a compile time error with our own error message. Doing this would allow us to control the error to suggest "try removing yield".

abstract class Operation

  def run
    {% raise <<-ERROR
           Operations must define `run` with no blocks or arguments.

           Try this...

               > remove yield from your run method
         ERROR
     %}
  end
end

The error message could use a little work, but that's the idea.

Maybe related: https://github.com/crystal-lang/crystal/issues/9771

Start by locating the Operation abstraction and the new operations implementation, then review the related Crystal issue #9771 for compile-time error behavior. Done means an operation that still defines run with yield receives a clear compile-time message suggesting that yield be removed, while valid operations continue to work.