tools: stricter no-undef eslint rule

By default eslint does not validate variables that are placed in a
typeof check.

PR-URL: https://github.com/nodejs/node/pull/19926


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>