Treat a property foo: () => void like foo = () => {}: as a method declaration.

[andy-hanson]

Fixes #1156

PR checklist

• Addresses an existing issue: member-ordering: function declaration mistreated as variable #1156
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update (may be needed, but current documentation doesn't seem to mention anything about Treat member variables initialized to a function as a function for ordering purposes #969)

What changes did you make?

Consider a property with a function type the same way as a property initialized to an arrow function.

Is there anything you'd like reviewers to focus on?

This is a breaking change, since people with this rule enabled will have to move all function-typed properties.
Maybe this should be put under an option. We can't really detect whether a property is meant to be used as an assignable field or as something to be mixed in to the prototype. However, it does seem more consistent with #969.

[adidahiya]

this is stale and there's not a lot of movement on the reported issue. closing for now; I think we can focus on other things