Include metadata in result objects about dsc

[SteveL-MSFT]

@michaeltlombardi would it be better to have executionType: whatIf instead? It would allow future execution types if any exist but I think it's more readable than true/false.

[michaeltlombardi]

I think executionType: whatIf is a good alternative. Mostly I kept it as a separate property to simplify object handling (the structure for the output object is the same for both whatIf and set in your proposal) and be more explicit, but it's straightforward to document that whatIf and set share a structure, too.

As you note, we might have other execution types, which could also be property keys or values, like executionType: rollbackOnFailure, executionType: stopOnFailure vs onFailure: rollback etc. I don't think either is more inherently extensible, but I'm open to executionType: whatIf being more readable.