src: rename fs_req_wrap -> FSReqWrapSync

This commit renames fs_req_wrap to FSReqWrapSync to make it consistent
with most of the other classes in the code base.

PR-URL: https://github.com/nodejs/node/pull/19614


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>