async_wrap: fix memory leak in AsyncResource

Reset the persistent that keeps the resource
Object alive when the AsyncResource is being
destroyed.

Fixes: https://github.com/nodejs/node-addon-api/issues/237

PR-URL: https://github.com/nodejs/node/pull/20668


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>
Reviewed-By: James M Snell <jasnell@gmail.com>