Define class elements in the correct order (#12723)

* Define class elements in the correct order

* Object.gOPDescriptors is not available on Node.js 6

* Handle numeric keys

* Update test

* Update fixtures

packages/babel-plugin-transform-classes/package.json

@@ -15,7 +15,6 @@
   "main": "lib/index.js",
   "dependencies": {
     "@babel/helper-annotate-as-pure": "workspace:^7.10.4",
-    "@babel/helper-define-map": "workspace:^7.10.4",
     "@babel/helper-function-name": "workspace:^7.10.4",
     "@babel/helper-optimise-call-expression": "workspace:^7.10.4",
     "@babel/helper-plugin-utils": "workspace:^7.10.4",