Spying on Getters and Setters post v2

[lucasfcosta]

The Problem

I was taking a look at #1205, and @muuki88 has noticed that we don't have a way to spy on getters and setters without having deprecation messages thrown at us.

The Cause

Before v2 we were just using wrapMethod and passing it a third argument that could be a descriptor.
Right now we are still calling wrapMethod when we pass a descriptor object as the third argument to the spy function (as you can see at this line).

My Suggestion

We should have a way to spy on descriptors since they can trigger important behaviors for objects and the way we currently have to work aroung this by using getOwnPropertyDescriptor().get and then passing it to stub().get is too hackish.

I think that in order to keep this API consistent with the stub api we must either do it the same way (which I think is bad) or spy on getters and setters by default. I think that by adding an extra argument we just end up going full-circle and doing the same thing we've just deprecated and by having another call after creating a spy it gets too cumbersome (this last argument is just based in my opinion lol).

I'd love to hear what other people have to say so that we can discuss and implement this if the maintainers agree it's needed.

If I missed something let me know, otherwise I'll be more than happy to implement changes.

[mantoni]

Can this be closed now?