async_hooks: stabilize part of AsyncLocalStorage

Mark AsyncLocalStorage constructor,
AsyncLocalStorage.prototype.getStore(),
and AsyncLocalStorage.prototype.run as
stable.

PR-URL: #37675
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Andrey Pechkurov <apechkurov@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Bryan English <bryan@bryanenglish.com>

Author: vdeturckheim