Cyberark refactor

[joseph-klein-cmm]

Summary

Adds the ability for secrets to be pulled from CyberArk, as well as AKV.

This includes a good bit of refactoring to avoid having to a) litter the code with type checks, and b) try to hijack the keyvault-based Secret object for storing CyberArk secrets. At a high level, the refactoring:

1. Abstracts the client code to allow an additional implementation for CyberArk
2. Moves the resource retrieval functions (GetSecret, GetKey, etc) to methods of the concrete Client objects.
3. Create a new Secret resource type that can be used for both CyberArk and AKV secrets