Improved test coverage for napi_make_callback by porting the
existing addons/make_callback test to n-api
PR-URL: https://github.com/nodejs/node/pull/12409
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
