RFR: JDK-8241463 Move build tools to respective modules

[Weijun Wang]

> On Mar 24, 2020, at 3:03 AM, Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com> wrote:
> 
> I have also moved the build tools to the org.openjdk.buildtools.* package name space (inspired by Skara), instead of the strangely named build.tools.* name space.

Is this really necessary? Skara is a standalone tool that have a public interface, but the build tools are entirely internal. They can even be non public.

--Max