Refactor the authentication module Connection.psm1 for scalability

[buidav]

💡 Summary

The old authentication works and is reliable but could use a refactor to better scale for additional authentication parameters, cross product authentication, and possibly for PowerShell 7 module switching purposes.

Will need to break out each individual authentication call into their own custom function and since now to config file defaults we won't be duplicating as much code if this was done earlier.

Motivation and context

Clean up the old code in Connection.psm1 for scaling for additional features.
#1208
#88

Implementation notes

Refactor Connection.psm1 to break out each authentication call into their own separate function, with room for scaling for additional authentication methods and cross product authentication when necessary.

Note that Exchange Online and Defender authentication functions were broken out into their own module because of an early technical reason with a Defender policy.

Acceptance criteria

Authentication code is refactored for better scaling for new features.

[schrolla]

Noted this as I was working on Defender related issue to pull tenant licensing related information that requires Defender to call Graph connection code which is not factored out yet. I refactored it there, so upcoming PR for issue #88 will likely be a stepping stone for this one.