Move CLI to Node.js v16

We should try to follow that latest Node.js versions closely and Node.js v16 is currently "active". This however comes with moving to NPM v7 - which has a host of changes (like package-lock format changing). I've run into issues using v16 locally and trying to run/debug the current project and deps (which expects v14).

Let's just pick a time and move across to v16 all together. 