PowerShell based DSCv3 resources

[SteveL-MSFT]

Summary of the new feature / enhancement

Recently it was identified that classes have a by-design limitation of not being supported in Constrained Language Mode (unless signed and trusted). Also, we want to have the PowerShell script called via pwsh -f and not pwsh -c as that ensures proper execution policy is applied. As a script, it would still need to be signed for full language, but some resources may work unsigned in constrained language.

Proposed technical implementation details (optional)

Need to think through how to define a structure in script so that the adapter can parse it appropriately and keep it easy for developers to author. For example, can we leverage comment based help here.