Model Impact of `set` for a resource

[SteveL-MSFT]

Summary of the new feature / enhancement

Applying set is an impactful operation, however, we may want a way to standardize how to advertise this beyond documentation (similar to PowerShell's ConfirmImpact).

Updating firmware may automatically reset the device (like a router would disconnect all clients) or setting sshd config would restart the service.

This is probably most useful for WhatIf (https://github.com/PowerShell/DSC/issues/70) to understand what can happen when applying configuration across multiple resources.

Proposed technical implementation details (optional)

No response