test: cover property n-api null cases

Add test coverage for passing `NULL` to each parameter of
`napi.*(propert|element)` and `napi_set_prototype`. In the case of
`napi_define_properties` also test setting various initializer fields
to `NULL`.

PR-URL: https://github.com/nodejs/node/pull/31488


Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>