Build: Require strict mode in Node.js scripts via ESLint

Build: Require strict mode in Node.js scripts via ESLint

So far, only browser-based JS files were required to be in strict mode (in the
function form). This commit adds such a requirement to Node.js scripts where
the global form is preferred. All Node.js scripts in sloppy mode were
converted to strict mode.

Closes gh-4499

(cherry picked from commit bbad821c399da92995a11b88d6684970479d4a9b)