test: add es6 module global leakage tests

* created testing es6 module for global leakage tests
* fixed a couple basic errors (vars -> lets, ...)
* added globals leakage detection to es module tests
* reversed whitespace change
* whitespace change reversed

PR-URL: https://github.com/nodejs/node/pull/16341


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>