Add Heap integration [CLI-158]

[Widcket]

Description

This PR integrates Heap to track the following events (only on production builds):

• The first login
• Every command executed that requires login

Testing

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not master

[cyx]

Just a commentary that we can't technically do wg.Add after we do wg.Wait -- that would cause a panic. As long as we're synchronously done doing all the wg.Adds before we Wait, it's fine.

There's other async style ways we can do this as well (e.g. utilizing a single channel, a single worker) to future proof against this potential issue.

[cyx]

Overall, just a minor potential issue with wg.Add / wg.Wait races, but 👍