This is the first step in removing the config dependency on "project".
This change is backwards-compatible because the value for this new
attribute defaults to the value from the provider.
If a given resource does not define an `Update` function, then all of
its attributes must be specified as `ForceNew`, lest Applys fail with
"doesn't support update" like #1367.
This is something we can detect automatically, so this adds a check for
it when we validate provider implementations.
Seth Vargo