[backflip]

This PR replaces chalk with node:util.styleText and mocha/assert with node:test/node:assert.

npx howfat -d before: 867 deps, 74.62mb, 28965 files
npx howfat -d after: 811 deps, 66.95mb, 28236 files

NOTE: This increases the minimal Node.js version from 16 to 20. However, Node.js 18 has been EOL for almost a year.

[alexleventer]

Thanks @backflip! I pulled the README --unmount-secret=name fix into main (24b7f32). Closing the rest for now: it conflicts with the Shopify tests added in #154, and util.styleText needs Node 20.12+, so engines: >=20.0.0 would let it crash on 20.0–20.11. Since this runs on users' machines during fly launch, we'd want to raise the Node floor on purpose rather than as part of a dependency cleanup.