buffer: move process.binding('buffer') to internalBinding

PR-URL: https://github.com/nodejs/node/pull/22370
Refs: https://github.com/nodejs/node/issues/22160


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>