Implement single factor authentication flow on 2fa-enabled iCloud accounts

[cody-somerville]

This pull request introduces support for single-factor authentication on iCloud accounts with 2FA enabled which permits access to find my services without completing 2fa flow.

1. Implement single-factor authentication flow on 2FA-enabled iCloud accounts
   Adds a new single-factor authentication flow that allows access to the Find My service and some account information without requiring full 2FA completion.

2. Refactor test/authenticate and update Find My tests
   Refactors the test/authenticate module to export a reusable authenticate function, allowing for customizable options to be passed to the iCloud service constructor. Updates test/findmy to utilize the new pause2FA single-factor authentication flow. Preserved REPL entry on direct execution of the authentication script,

3. Improve error handling and logging for Find My service
   Instead of throwing uncaught json parse error on authentication timeout, more gracefully log and throw more meaningful exception.

[ludufre]

I had to comment the call of await this.checkPCS(); inside _getiCloudCookies() because that call is returning HTTP 422