n-api: Retain last code when getting error info

Unlike most N-API functions, `napi_get_last_error_info()` should not
clear the last error code when successful, because a pointer to (not
a copy of) the error info structure is returned via an out parameter.

Backport-PR-URL: https://github.com/nodejs/node/pull/19447
PR-URL: https://github.com/nodejs/node/pull/13087


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>