async_wrap: expose enable/disablePromiseHook API

Allow node::PromiseHook (src/async-wrap.cc) to be enabled/disabled from
the JavaScript API.

PR-URL: https://github.com/nodejs/node/pull/13509


Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>