This is some cleanup that has been needed for a while.
There's still one more step that could usefully be done, which is to
split up our api package into the part that provides the helper
functions and the part that provides the internal types. That can come
later.
The v1beta1 package is now a good example of what an api plugin should
do to version its types.
Currently all registry implementations live in a single package,
which makes it bit harder to maintain. The different registry
implementations do not follow the same coding style and naming
conventions, which makes the code harder to read.
Breakup the registry package into smaller packages based on
the registry implementation. Refactor the registry packages
to follow a similar coding style and naming convention.
This patch does not introduce any changes in behavior.
