New Cop to disallow use of _() in constants.

[Fryguy]

Is your feature request related to a problem? Please describe.

It's not uncommon for new users of gettext to use _() in constants, not realize that will translate at first load and not on demand. This is easy to miss in code review.

Describe the solution you'd like

I'd like to see a Cop that checks for usage of _() in constants. Secondarily, if it's possible, it would useful to also detect memoized usage of _() in a class methods or global context.

Describe alternatives you've considered
Additional context

None