inspector: fixed V8InspectorClient::currentTimeMS

On inspector side inside V8 we assume that this method should
return number of ms since epoch.

PR-URL: https://github.com/nodejs/node/pull/21917


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>