test: test doc'd napi_get_value_int32 behaviour

We chose to document this in the docs as there are
different possible behaviours.  Adding this test to validate
that all vm implementations do it the same way.

PR-URL: https://github.com/nodejs/node/pull/12633


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>