doc: fix a few n-api doc issues

- Add doc for napi_create_string_latin1().
- Fix signatures where c string was specified instead of napi_value.
- Fix return type of napi_callback.
- Update to specify that napi_escape_handle() can only be called once
  for a given scope.

Backport-PR-URL: https://github.com/nodejs/node/pull/19447
PR-URL: https://github.com/nodejs/node/pull/13650
Fixes: https://github.com/nodejs/node/issues/13555
Fixes: https://github.com/nodejs/node/issues/13556
Fixes: https://github.com/nodejs/node/issues/13562


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jason Ginchereau <jasongin@microsoft.com>
Reviewed-By: Ingvar Stepanyan <me@rreverser.com>