This uses knip (https://knip.dev) to check dependencies, in hopes of avoiding
issues like open-telemetry#2473. This adds 'npm run lint:deps' and adds that to the
existing 'npm run lint'.

This change includes fixes for a handful of unused and unlisted deps.
For now knip is configured to only check 'production' deps. Checking non-prod
deps results in way too many false positives.

…ion.ts files

…the top-level

After reading more about how npx works
(https://docs.npmjs.com/cli/v8/commands/npm-exec)
I'm more confident that running knip via npx (to workaround the
install-tree issue) is fine for dev and for CI.