Fixes related to TISTUD-4119 Improve beta/rc update process

- Allow getting the full list of available versions for an NPM package using #getAvailableVersions
- Remove INodePackageManager#getVersions and use #getAvailableVersions instead - it actually works
- Make #getInstalledVersion and #getAvailableVersions both use --json true args to force json output and then parse the output as JSON for more robust output handling.