[7.0] Deprecate babel-core/register.js (#5132)

* Deprecate babel-core/register.js

* add error when using `babel-core/register`

packages/babel-core/register.js

@@ -1,3 +1 @@
-/* eslint max-len: 0 */
-// TODO: eventually deprecate this console.trace("use the `babel-register` package instead of `babel-core/register`");
-module.exports = require("babel-register");
+throw new Error("`babel-core/register` has been moved to `babel-register`.");

packages/babel-core/test/fixtures/browserify/register.js

@@ -1,3 +1,3 @@
-require("../../../register")({
+require("babel-register")({
   ignore: false
 });