test: add unhandled rejection guard

Add an unhandled rejection function in
addons-napi/test_promise/test.js. Also, add a
rejection handler to catch the unhandled rejection
after introducing the guard and test the reason
code.

PR-URL: https://github.com/nodejs/node/pull/17275


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>