fix(npm): avoid loading installer deps before they exist

- lazy-load node-fetch, cli-spinner, inquirer, and find-process in dist/npm/index.js
- switch get-latest to built-in https so it can run without local node_modules
- keep postinstall working when find-process is not yet installed
- prevent npm global install from failing during prepare/postinstall in a clean checkout

Signed-off-by: Ryan Swanson <ryan.swanson@loft.sh>