Reduce all uses of Unstructured to the simpler form, and avoid asking
for mapper or typer unless it is required. Use Typed() for places that
previously used VersionedObject, and remove paths for versioned objects
from code that is now using unstructured.
Previously, the fake RESTClient in client-go required a Registry. It
used the Registry to fetch the GroupVersion for the fake client.
However, the way it did so was dubious in some cases (it hard-coded the
default API group in places), and not strictly necssary.
This updates the fake client to just recieve the GroupVersion and
internal group name directly, instead of requiring a Registry, so that
it can be consumed in unit tests where a Registry isn't necessarily
readily available (e.g. elsewhere in client-go).
**What this PR does / why we need it**:
Visibility rules allow dependency control. The rules currently in
place make all targets public, to override the default state of
private. This PR removes public visibility from kubectl code. It
uses specially named pacakge groups to identify "bad" dependencies on
kubectl code for later refactoring or removal.
**Which issue this PR fixes**
First in a series of PRs to address kubernetes/community#598
**Release note**:
```release-note
NONE
```
