src: rename req-wrap -> req_wrap

This commit renames req-wrap to req_wrap consitency with other
c++ source files.

PR-URL: https://github.com/nodejs/node/pull/17022


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>