Move subclass inheritance to end (#7772)

We were using `Object.create` to setup the prototype chain at the start of the class definition, which lead to #7771.

I was a bit worried about a speed hit, but it seems everyone optimizes the two patterns the same way.
https://jsbench.github.io/#f9fca52407643d96458a35763b201215

Fixes #7771.

packages/babel-plugin-transform-function-name/test/fixtures/function-name/modules-3/output.js

@@ -10,8 +10,6 @@ var _store = require("./store");
 let Login =
 /*#__PURE__*/
 function (_React$Component) {
-  babelHelpers.inherits(Login, _React$Component);
-
   function Login() {
     babelHelpers.classCallCheck(this, Login);
     return babelHelpers.possibleConstructorReturn(this, babelHelpers.getPrototypeOf(Login).apply(this, arguments));
@@ -23,6 +21,7 @@ function (_React$Component) {
       return (0, _store.getForm)().toJS();
     }
   }]);
+  babelHelpers.inherits(Login, _React$Component);
   return Login;
 }(React.Component);